It is untrue that all is fair in love and war. Especially in war. There are a considerable number of treaties governing the conduct of war. War Is Hell, but now even this Hell is developing a lot of standards. Here are just a few samples, The Other Wiki has a more comprehensive list:
- The Strasbourg Agreement (1675) where some countries agreed not to use chemical weapons.
- The Hague Convention (1899) [and the second Hague Convention (1907)] that led to rules of declaring and conducting warfare.
- The Geneva Conference (1925) led to the banning of chemical weapons during war.
- The Biological Weapons Convention (1972)
- The 1993 Chemical Weapons Treaty further banned certain chemical weapons.
- The 1997 Ottawa Treaty on anti-personnel land mines
- The Convention on Certain Conventional Weapons (1980) prohibits undetectable weapons (explosive devices made of all plastic which defeat metal detectors); mines and booby traps; firebombs and incendiary weapons; blinding lasers; or recycling used unexploded ordnance from previous wars.
In fact, having rules on what countries (and, by extension, their militaries) can do in times of war is considerably Older Than Dirt, as even non-literate, stone age peoples have usually had customs and taboos strictly limiting what may be done in war, and Hugo Grotius' classic On the Laws of War and Peace (1625) cites back to ancient Greek and Roman sources for many of its rules.
Thus, war has usually been governed by some sort of law or custom throughout history, but they differ in various times and places. As noted below, the Geneva Conventions recognize the right of a POW to attempt to escape. During the Napoleonic Wars, as an example, if a captured officer swore an oath to his captors that he would return home and no longer participate in the war until its resolution, he was honourbound to keep his word. Many imperialist victories throughout history can be attributed to two different sets of customs regarding war coming to a head.
Note that this article is written primarily from an American perspective—while the international laws of war are just that, several parts of the article reference policies implemented in the USA, but not necessarily elsewhere.
A quick way to show that a killer is really a bad guy is to have their bullets having a cross cut into the tip. This will cause the bullet to expand when it enters the body, causing far more damage. Since hollow points are permitted in most non-military applications and are more reliable (jacketed dum-dums have a disturbing tendency to leave the jacket in the barrel of the gun, never mind the fact that they don't expand that reliably) dum-dums are usually used to show how bad someone is. Or that setting predates the invention of hollow points. Named after an arms factory in India, by the way.
In 1899, the Hague Convention stipulated that bullets must not be designed to expand or flatten within the body, causing grievous harm. This has been a contentious point, as modern rifle calibers often yaw or tumble within tissue due to their velocity and shape, and this behaviour has been encouraged with both 5.56x45mm NATO and 5.45x39 rounds by selectively weakening the full metal jacket in certain portions or the addition of an air pocket, while the British were doing this all the way back in 1910, designing the .303 British Mk VII, a full metal jacket round with the front part of the core made of aluminum.
Although the example points out the dum dum rounds as the specific example, the laws of war generally state that the use of altered projectiles is not permitted, including the use of glass projectiles, as well as exploding projectiles below a certain size.
HollowpointsThese bullets, which expand in a person's body, are prohibited in formal warfare, but allowed in domestic law enforcement and actually required in some jurisdictions for hunting. Their downsides are that they have poor performance against armour and barriers as well as sometimes not expanding correctly. In addition, automatic or semi-automatic weapons capable of reliably feeding hollowpoints are a relatively recent invention. Their upsides are their relatively low chance of overpenetration and causing collateral damage behind your target, and of course increased stopping effectiveness.
Match grade ammunition (such as Sierra MatchKing) often contains a thin hollow nose for ballistics reasons, but since its wound profile is not noticeably different from a normal FMJ wound, the U.S. military has authorized its use.
The reason behind the ban on both hollowpoints and Dum-Dums is the idea that military weapons should serve a military purpose, and no more. That is, follow the idea of Least Suffering—a weapon should cause the minimum amount of damage to incapacitate a person, and no more, or kill someone quickly, rather than maim. Intentionally maiming an opponent serves no moral purpose that a "normal" wound wouldn't, and therefore is excessive, and banned. In reality, at least in modern ammunition design, expanding ammunition is designed to kill the target faster, though that's not what the thinking was in 1899.
When the U.S. Army adopted its "Modular Handgun System" (Sig Sauer's M17 semi-automatic handgun) in 2019, it chose to include hollow point ammo as an option for the pistol, for the same reason that US law enforcement does: a pistol is a self-defense weapon used in extreme circumstances, and hollow points are more effective in stopping the threat while, at the same time, being less likely to go through the target and hit whatever's behind him or her.
Tear GasTechnically not illegal, but strongly discouraged for fear of reprisal with deadly chemical weapons. Oddly enough, use of tear gas is banned in normal warfare but legal for use by civilian law enforcement. It's also legal to tear gas your own troops as part of their training. Citing how common Urban Warfare is in the modern War on Terror, many U.S. service members have begun to criticize the arbitrary ban on tear gas, as it would actually save lives lost on both sides in deadly house-to-house fighting by forcing the occupants out into the open where they can be sorted out non-lethally. However, there is justification, as while in police situations the police is unlikely to have access to deadlier nerve gas, in the military there is a risk that the command would use tear gas as an excuse to deploy the deadlier version of tear gas and lying to the grunts that they are carrying tear gas and to use nbc safety gear when deploying it.
CombatantsWounding or killing combatants is not a war crime. Combatants are people who fight (e.g. infantry) or directly assist those fighting (e.g. logistics personnel). Wounding or killing noncombatants, i.e. civilians, is a war crime. That means, for example, a computer programmer or network technician setting up a military network is a legitimate military target, but a programmer or tech setting up a computer network for a news bureau, even though they are filming in a war zone, is not. This is why anyone who works in a combat or combat logistics position wears a uniform while on duty even if they are not in a combat area, so that combatants and civilians are clearly distinguished. Wounding or killing combatants who have surrendered, are leaving damaged vehicles (except tank crews leaving damaged tanks), or become 'hors de combat' ("outside the fight," i.e. incapable of fighting) all constitute war crimes. It is a war crime for a combatant to disguise themselves as a civilian with the intent to attack, but disguising themselves for any other reason, including desertion and escape, is perfectly legal.
While civilians are allowed by the Geneva Conventions to take up arms as militia against an invading army, they must still abide by the Geneva Conventions in their own behaviour, be "carrying arms openly", and do their best to have "a fixed distinctive sign recognizable at a distance" in order to still enjoy the protection of the Geneva Conventions for themselves. The intent of this particular section of the Geneva Conventions is to make the distinction between combatant and noncombatant immediately obvious at a distance so as to minimize noncombatant casualties by letting the enemy be able to know which people are fighting them and which ones are just bystanders. The "illegal combatant" distinction generally comes into play when that distinction is deliberately being abused.
There are several quasi-military jobs that were taken into uniformed services to give protection under the Geneva convention to those workers. Otherwise they were unlawful combatants and possibly spies. The Public Health and NOAA Corps are American examples of battlefield surveyors and ambulance personnel put in a uniform to give them protection on a battlefield.
Also note that medics and similar positions are permitted to carry small arms solely for self-defence (though, many chose not to). In particular today, when medics are integrated into the unit as a soldier first, medic second, most do not wear a Red Cross/Red Crescent symbol and do carry weapons. Also, even specialized actual medics are permitted to carry and use weapons against those who would attack those under their care; e.g. if the enemy is harming the wounded (itself a war crime), medics are entirely justified in responding with lethal force. In these cases, they are considered lawful combatants, and are not war criminals for carrying weaponry. See below for other cases where medics are treated differently.
It is worth noting that the Convention only names lawful combatants and noncombatants directly. Unlawful combatants are a US interpretation, based only partly on the Geneva Convention.
Deliberately wounding or killing civilians is a war crime, as is issuing or obeying orders to wound or kill civilians. This is subject to some fine distinctions, however; if civilians are in or near a legitimate military target, it is not generally considered a war crime to destroy the target in the absence of other options. This is how it was not considered a war crime for the various belligerents during World War II to go around bombing each others' factories—the factories were generally producing either war materiel or other items necessary or useful to the war effort, and thus the fact that the workers were civilians was considered less important than the military character of the goods they produced. More contentious was, first, the London Blitz and, later, the RAF and US Army Air Force's 1944-45 attempts to more efficiently destroy factories and rail hubs by creating firestorms in the urban areas around them, and the Luftwaffe and RAF's attempts to create firestorms in urban areas with no industrial plant or rail infrastructure in order to 'demoralize' enemy populations unarguably constituted war crimes.
Moreover, the rule against killing or wounding civilians does not extend to seizing or destroying their property; examples from the 20th century wars are innumerable, but perhaps the best known incident in the USA's history was was General William Tecumseh Sherman's 1864 'March to the Sea' that wrecked Georgia in September-December 1864 (and later campaigns in the Carolinas in early 1865) during the The American Civil War (a war fought largely in accordance with the modern rules of war). Vast quantities of civilian property (including railroad infrastructure, manufacturing facilities, manufactured goods, cotton, private homes, and especially food and slaves) were seized and destroyed (the food was eaten, the slaves were set free, and the rest was either burned or reduced to rubble) while relatively few civilians were actually killed. Sherman's side won, so he would never have been prosecuted for this campaign anyway (instead, they wrote an infuriatingly catchy song about it), but if he were magically resurrected and placed on trial before a fair tribunal, he would almost certainly be acquitted, as his property-destruction acts would even today be considered cruel but not illegal, and tracing any of the civilian casualties directly to his orders would be virtually impossible.
Again, obeying orders in killing civilians doesn't make it not a war crime. One example of what not to do is the German Military (Wehrmacht)'s 13/5/1941 'Barbarossa Decree'. Section I.4 mandated that:
"Collective drastic action will be taken immediately against communities from which treacherous or insidious attacks against the Wehrmacht are launched, on the orders of an officer with at least the rank of battalion commander upwards, if the circumstances do not permit a speedy apprehension of individual culprits."
There was a distinct difference in the interpretation of this order in 'the east' and in 'the west'. In countries with racially acceptable populations which were to become German puppets after Germany won, it was often interpreted to mean 'the deportation of the male population for slave labour'. In countries with racially undesirable populations which were to be largely or totally eliminated to make room for German settlement, it was understood as 'death for 100 civilians for every member of the military killed by partisan action.' More understanding local commanders would consult with local leaders and attempt to fulfill their quotas using 'inessential' members of communities such as Jews or Romani (before they were deported in 1942), disabled or mentally ill people, gays, the elderly, or children. In roughly that order.
After the war the Poles and Soviets attempted to have the German commanders in Anglo-American custody who had enforced these orders tried for war crimes. They were partially successful in that some of the actions of some figures, even a few of the ones important to the rearmament of West Germany including Heinz Guderian, were eventually investigated by US and British commissions. Ultimately a full thirteen of these people (including Marshalls Kesselring and Manstein, who had been in British custody) were convicted of War Crimes and served up to five years in jail before their early release for reasons of 'good behaviour' and 'poor health'.
Persons parachuting from disabled aircraftUnder Article 42 of the First Additional Protocol to the Geneva Conventions (1977), aircrews parachuting from disabled aircraft are not to be fired upon, as they are already out of the fight and now completely helpless to defend themselves. In the European Theatre during World War II, any pilot who intentionally fired at parachuting aircrews in sight of the enemy effectively signed their own death warrant (except on the Eastern Front, where the Soviets deliberately refused to follow the laws of war and the Germans retaliated in kind). Any enemy fighter pilots in the area would ditch all other priorities just to take the son of a bitch down.
The prohibition of shooting aircrews parachuting from disabled aircraft does not apply to the dropping of paratroopers who may be fired upon during their descent, whether their aircraft is in distress or not. Belligerents must distinguish between those who are bound upon hostile missions (such as paratroopers entering into combat areas to fight enemy forces and/or destroying enemy supply lines) and those who are not (such as aircrews parachuting from disabled aircraft as they are out of combat and are not descending for hostile purposes).
Name, rank and number—Prisoners Of War
There are actually four Geneva Conventions—number three being the relevant one for POWs.
Being taken prisoner
If a group of soldiers decides that they want to surrender, they should make their intentions clear. This usually entails waving a white flag (or something big and white) or raising your hands.note Black flags are also used for this purpose, but are more rare. This caused some awkwardness when Iraqis tried to surrender to Americans who were unaware of the custom. Faking surrender as a trap is a war crime in itself, known as "perfidy", and will be discussed in more detail later.
Once the other side captures you, they are allowed to search you and restrain you. They can confiscate your pack animals (these are still used in less developed parts of the world where motorized transportation has problems, particularly in rugged/mountainous terrain), weaponry and any military documents. However, a prisoner must be permitted to retain his personal protective equipment, such as helmets and gas masks. And, once a prisoner has been captured, his health, safety, and well-being is the responsibility of his captors.
Any unit of any armed force in an untenable situation may surrender, from an individual soldier to a platoon to a whole division to the entire armed forces of a state (at which point that state is deemed to have ended its participation in the conflict). A surrender can be under conditions or unconditional, the latter meaning that only international law applies. The Allies in World War Two demanded—and got—an unconditional surrender from Germany.note It has been argued that the end of the war in Europe is also a case of debellatio, completely destroying a hostile state, as Nazi Germany ceased to exist.
The only things that you are obliged to tell the people capturing you are your name, rank, serial (or service) number and date of birth. The US permits provision of relevant health and welfare information too (e. g. blood type, allergies, that kind of thing, as well as religious preference, since good captors are supposed to accommodate worship requirements and dietary restrictions). Telling more may result in a court martial if and when you get home. Nevertheless, your captors are permitted to offer positive inducements—better food/living conditions, less/easier work, money—for providing intelligence. They are not allowed to take you away for interrogation; you must approach them (which means you run the risk of more immediate vigilante punishment from your comrades as well as penalties back home). Negative inducements are strictly prohibited (see below).
Also, there is some confusion (and a bit of a grey area) as to when surrender is allowed. Most nations consider that the attacker is given some discretion at this point, as to when a surrender is valid. For example, if a soldier is actively firing a weapon at an enemy, when another enemy walks up behind them and does a *Click* Hello. Even if the soldier turns around with his hands up, it's at the capturing enemy's discretion as to whether or not to accept this as valid. Most nations would consider the capturing enemy fully justified in shooting the soldier, even though they were surrendering, since they were actively engaged in fighting up until the instant where they perceived they were compromised. That is, most nations require that surrendering forces do so before the very last instant, where it's perceived as an attempt to inflict maximum damage on the capturers while avoiding the consequences.
— Article IV of the Code of the U.S Fighting Force
Once taken to a camp (these have to be designated in a way that aircraft can see them and should be well away from the front line), prisoners are to be well treated. (How well they were treated made headlines when the fate of Vietnam War prisoners became common knowledge, but the Vietnamese could just point out their own civilian population endured similar misery in their everyday life back then and North Vietnamese prisoners were treated even worse.) They are allowed to write letters home and receive them—although the captors are allowed to censor these communications, so long as it is done reasonably quickly—The Red Cross can send them parcels with food and religious freedom is allowed. You also are allowed pay in line with your rank.
Being forced to work
Prisoners of war can be compelled to work, but only in non-military capacities, which includes a blanket ban on any work involving chemical production. Farm work is a common one for this.
You cannot be forced to do dangerous or unhealthy work. Officers and NCOs cannot be compelled to work, but may agree to do so if they wish.
Medical personnel and chaplains must be permitted to work in those roles, and must not be forced to perform any other. However, medics and chaplains can be put to the care of prisoners other than those from the nation they represent if necessary. They also remain bound by the ethical requirements of their professions, meaning that they may need to minister to the enemy in an emergency.
Torture of anyone in any way is a war crime
Article 75 of the First Additional Protocol to the Geneva Conventions (1977) contains a prohibition of torture as one of the basic minimum protections applicable to everyone, even if they are eligible for protection under none of the other Geneva Conventions. The "legitimate" in the header above refers to the fact that under the original Geneva Conventions, there are protections only for lawful combatants and noncombatants, not "unlawful combatants". In other words, torturing unlawful combatants (along with anyone and everyone else) is a war crime.
The US has never ratified the First Additional Protocol, but did sign and ratify the UN Convention Against Torture, which bans the use of torture in all circumstances against all possible prisoners, and also mandates that signatories prosecute anyone who violates the convention within their jurisdiction. The exact working definition of torture is... contentious.
Realizing that the people it fights have frequently not adhered to Geneva (as seen in World War II, the Vietnam War and every other conflict since 1941), the United States military, plus others, trains its aircrew (along with others particularly likely to end up behind enemy lines, such as special forces) in torture resistance techniques, including "waterboarding" them.
The use of prisoners for medical experiments is also a war crime, unless it is clearly for the prisoner's well being.
Prisoners are permitted to escape (many belligerent forces see it as a duty to do so) and executing them or anyone else for attempting to do so is a war crime. It's not a war crime to wound or kill prisoners attempting to escape, provided you give them a clear warning first.
Medical and religious personnel are generally exempt from requirements to attempt escape, as their specialties are typically more valuable to the remaining prisoners than any potential harm done by their escape.
Medics and chaplains
Medical personnel and chaplains, being noncombatants, are not technically prisoners of war, though they must receive as good treatment as the prisoners. Furthermore, they must be permitted to carry out their ministrations. They can be required to minister to prisoners from other nationalities, however, and are still bound by professional and ethical obligations that may compel them to minister to the enemy in an emergency.
Geneva III in its 1949 revision, states the requirements for someone to be considered eligible to be a POW:
(a) That of being commanded by a person responsible for his subordinates;
(b) That of having a fixed distinctive sign recognizable at a distance [a uniform or something that allows identification];
(c) That of carrying arms openly;
(d) That of conducting their operations in accordance with the laws and customs of war.
Mercenaries, even if they are uniformed regular units conducting operations in accordance with the laws and customs of war, are still specifically not covered by the Geneva Conventions as specified by Article 47 of the First Additional Protocol to the Geneva Conventions (1977). Terrorists are not covered by the Geneva Conventions—they fail eligibility under Geneva III because of their failure to meet the standards listed abovenote , and they are not covered as civilians under Geneva IV because Geneva IV does not apply to individuals taking a direct part in ongoing hostilities; only to noncombatants and similar. In addition, the usual tactics of terrorists, most especially random attacks against noncombatants, are themselves acts specifically proscribed by Geneva IV. However, article 75 of the First Additional Protocol establishes certain very basic minimum protections that apply to everyone regardless of whatever categories of eligibility they may or may not qualify for, including terrorists/unlawful combatants.
Mercenaries that are an integral part of a given State's military system (Gurkhas, Foreign Legionnaires, etc.) are not considered mercenaries for this purpose even though they are in fact soldiering for a foreign state, which is a common definition of "mercenary".note A captured Legionnaire would be covered by the Convention.
The 1949 version also covers spontaneous resistance movements, even not in uniform, if their conduct abides by the laws and customs of war. However, they are not exempt from the four basic requirements at the top of this subheading and most classic resistance movements deliberately avoid using uniforms or identifying symbols, thus forfeiting their protection and leaving them liable to be shot as spies or saboteurs. Many resistance actions, such as sabotage or bombing, also fail to be 'carrying arms openly'. A resistance movement that did fulfill all the requirements, even just to the point of using coloured armbands during their overt attacks, should still qualify.
It is a war crime to order soldiers to kill prisoners, and for soldiers to kill prisoners whether ordered to do so or not. An infamous example of this is the 'Commissar Order', issued to the German military on 6/6/1941 (rescinded on 6/5/1942 when increased Waffen SS presence made it unnecessary for Wehrmacht personnel to continue handling these actions themselves). Section 2 states:
"The originators of barbaric, Asiatic methods of warfare are the political commissars. So immediate and unhesitatingly severe measures must be undertaken against them. They are therefore, when captured in battle, as a matter of routine to be dispatched by firearms."
A more infamous order, which applied not just in the occupied Soviet Union but across the entire European theater of war (and even applied to some people who spoke English, making it famous in the Anglosphere) was the 1942 'Commando Order' (which remained law until Germany's cessation of existence). Section 3 states:
"From now on all men operating against German troops in so-called Commando raids in Europe or in Africa, are to be annihilated to the last man. This is to be carried out whether they be soldiers in uniform, or saboteurs, with or without arms; and whether fighting or seeking to escape."
Both orders are illegal now and were illegal at the time, although the preamble to the 'Commissar Order' had claimed that the Geneva Convention did not apply to the Soviet Union and its citizens because the USSR was not a signatory of it. The Soviets had signed it, but even if they hadn't then ordering prisoners to be killed would still have been illegal. After the war the Soviet Union pushed to have German officers in Anglo-American custody who had implemented those two orders (on Eastern Bloc citizens) tried for war crimes. The British and Americans complied in several cases, and Erich von Manstein was famously convicted for enforcing elements of both Orders (killing POW, NKVD/NKGB special forces, partisans, civilians in 'retaliatory deterrence', and Jews, for a total at least in the tens of thousands), only to be released from prison after serving 4 years of his 18 year sentence for 'good behavior'. note
Showing Your True Colours
Despite a more general prohibition on dressing as the enemy these days, this is still a permissible action.
A ship is allowed to fly the flags of an opposing or neutral nation (although protected symbols are banned) as it approaches an enemy vessel or the coast. However, before it engages the enemy, it has to lower the colours it is flying and reveal its true colours. Witness the Q-Ships of World War One and World War II, converted merchant ships loaded with things which float like cork, balsa and wooden coffins to render them nearly unsinkable—and also large artillery hidden by drop-down panels. When an enemy submarine approached to close range and surfaced to attack with a deck gun, the colors were raised, and the panels were dropped.
Lowering your colours (called "striking") is the naval symbol for surrendering. This is also the origin of the expression "nailing one's colours to the mast", meaning you weren't going to surrender.
This is not as relevant these days—it's a lot harder to disguise a particular cruiser type than a sailing ship and naval warfare these days takes place at far longer ranges. There is a story of a British aircraft carrier pretending to be a Pakistani cruise liner on radar (by broadcasting such a registration beacon and answering hails in Urdu) in order to sneak up on some Americans during a training exercise. The USN was only alerted to the deception when the British opened fire. When they protested that the British should have announced their identity beforehand, the British argued that they had been flying the physical Pakistani flag the whole time (see the note), and raised the physical White Ensign when they launched... but of course, the USN was too far away to see them. note
This applies also to ground troops, who may wear enemy uniforms as a deception but before firing upon enemy forces, they must put on proper insignia so that if they are captured, they are entitled to be treated as prisoners of war. However, as lawful combatants can still be tried for any criminal offences they commit in the execution of their duty (rape, theft, etc.), if they are captured using enemy uniforms to gather intelligence/spread despondency or falsehoods within the ranks of the enemy behind enemy lines, they may be tried for espionage and, if found guilty, executed or otherwise punished as per the laws of the nation that has captured them.
This archaic-sounding term is used to refer to a number of illegal activities that all relate to somehow taking advantage of an enemy's magnanimity or compliance with the laws of war in order to attack them. All of the following are war crimes, both because they are generally unpleasant and because they encourage the enemy to engage in ruthless and immoral behaviour:
- Feigning an intention to surrender in order to attack the enemy.
- Pretending to be dead or seriously injured in order to attack the enemy.
- Pretending to be a civilian (see above under "combatants").
- Note that the last two are only illegal if you're going to attack. Doing these in order to desert or to escape the battlefield are not illegal (but your own side will, of course, shoot you—presumably after a trial, we hope—if they catch you deserting).
- Pretending to be UN forces, members of the Red Cross/Red Crescent, or other international organisations. Note that if the UN is running a military operation (e.g. The Korean War), you're allowed to use their logo on your tank... it's when the UN doesn't give you permission and you use it that you're running afoul of Article 38.
- Pretending to be armed forces of a neutral state.
- Pretending to be members of enemy armed forces in a combat situation. Note that the use of enemy uniforms for reconnaissance or intelligence-gathering purposes is not perfidy—although the enemy are still allowed to shoot you for espionage if you get caught.
It is not acceptable to say "I was just following orders".
— Principle IV of the Nuremberg principles.
If a member of the armed forces followed an order to commit an act which clearly constitutes a war crime under the laws of war, they are every bit as responsible for it as the superiors who ordered them to do it. During the Nuremberg and High Command trials many military officers unsuccessfully used the "I was just following orders" defence—afterwards known as the Nuremberg Defence—in a bid to avoid harsh sentencing. This is because, somewhat stereotypically, under pre-war German law the most severe category of murder (and its attendant sentences) was reserved for those committed for emotional reasons (hatred, anger, love). More generally they (successfully) strove to convince the press and public that they had been victims of the Nazi regime too. However, the Allied judicial panels were interested in prior intent and not their exact motivations. Hundreds of military personnel, including a dozen high-ranking officers, were convicted of war crimes and served prison sentences of up to five years.
That said, subordinates only share in the moral responsibility for committing war crimes if they wouldn't be punished for refusing to commit it. Punishment in this context means execution, torture, and under some interpretations imprisonment. If they are threatened with such punishment, then they don't share in the moral responsibility for committing the crime and can't be convicted for it—after all, not everyone is cut out to be a martyr, and even if in hindsight we find the decision repulsive, we can sympathize with a person (probably a terrified young person) for deciding to follow horrific orders when the alternative is death, torture, or extreme deprivation.
However, if a soldier is ordered to commit a war crime but will not face any punishment for refusing, they bear full responsibility for the act. Note that the 'punishment' of being transferred from an active sector like Ukraine or Serbia (with high pay and opportunities for rapid promotion) to another unit, even if that unit is in a 'quiet' sector like occupied Denmark or training bases in Germany, is not considered punishment for these purposes. This is why German military officers were indicted at Nuremberg and the High Command Trials: German military personnel could almost always refuse to participate in war crimes without any adverse consequences, and the hierarchy would just find someone else to do the job. Because the option of refusing was always there, a handful of German officers of all levels were brought to trial and convicted for issuing or obeying illegal orders .
Most military bodies now train their military personnel to follow legal orders and require them not to obey illegal orders.
While actual enforcement of these laws takes place through a wide variety of mechanism (international NGO's, UN and regional bodies etc.), the biggest incentive to follow these rules is The Golden Rule. If you do not follow the rules, the enemy most certainly will not. This is especially true in the case of treatment of POWs: if you mistreat enemy troops over whom you have total control, the other side will lose any compunctions about mistreating your service members that they have captive. This is one of the reason that armed forces personnel are rather keen on these rules.
The history of war is replete with examples where a relatively small-scale breach of the rules regarding the killing of POWs or shot-out airmen resulted in massive retaliations by the other side. To give a pair of WW2 examples: A Japanese fighter machine gunning a bailed-out B-17 crew and killing eight of the thirteen at Bismarck Sea resulted in the US and Australians sinking the lifeboats and rafts of the convoy after it was destroyed, killing thousands of Japanese soldiers; during the Battle of the Bulge the murder of a group of American prisoners by the SS caused a number of American units to refuse to accept surrenders during the course of the battle, costing hundreds of German lives. Worst of all, public opinion compelled the USA to prosecute the junior SS officers responsible in the postwar trials process. This gave the Soviets a 'foot in the door' when arguing for the prosecution of more senior officers responsible for War Crimes.
A ceasefire simply means a temporary cessation of hostilities, whether in one sector (for allowing prisoner exchanges, collecting of the wounded) or theatre-wide (usually as prelude to the cessation of the conflict as a whole) , while an armistice is the wartime equivalent of the end of the fighting stage before the final resolution, it means in essence that sides are recalling their Generals and sending in the diplomats.
Ceasefires take effect at a set time after the agreement, allowing the word to get to troops in the field. In practice, people generally stop firing once they're told of the ceasefire; no one wants to be the last to die in a war. Although, this might not be the case when it is unclear whether the ceasefire is the actual end of the war. As a ceasefire usually entails that the battle lines will remain where they are, people might attempt to use the time period to get a favourable positions. Standing orders of the Pakistan Army are that Pakistani forces will continue to jockey for favourable positions until the coming into effect of the ceasefire (although major offensives are forbidden) while the Israeli Army seems to have a policy (if not formal orders) which is similar. This is a risky proposition, the enemy might decide to simply abandon the plan.
There might be a clear winner or loser at the end of an armistice; what matters is that the sides have only agreed to stop fighting until further notice. Generally speaking, an armistice is when the war has clearly ended. Usually, peace talks and a peace treaty immediately follow but the term "peace treaty" is something of a misnomer: a peace treaty is actually about restoring (or establishing) diplomatic recognition and ties, as well as settling at least some of the disputes that led to the war in the first place (generally in the victor's favour, assuming that there is one).
Note that a peace treaty need not follow an armistice: countries can agree to stop fighting without agreeing to establish diplomatic ties or settle their issues. As a result, armistices can last for a very long time, during which the sides remain technically at war. Three notable long-lasting armistices exist today:
- The armistice ending the Korean War was signed in July 1953, but no peace treaty will be signed in the foreseeable future. North Korea has technically withdrawn from it, several times in fact, but all parties treat it as extant.
- The ArabIsraeli Conflict presents an interesting situation, where three wars were fought, each of which ended with an armistice. However, of the Arab states fighting these wars, only four—Egypt, Syria, Jordan, and Iraq—directly participated in all of them. So:
- Egypt and Jordan both have signed peace treaties with Israel. Armistices most recently existed between Israel and Egypt 1973-1979 and between Israel and Jordan 1973-1994.
- Syria and Iraq have not signed peace treaties, and thus have armistices but are still technically at war with Israel. Barring a sudden resolution of Israel's problems with the Palestinians, treaties seem unlikely in the immediate future.
- Lebanon's last active and official participation in a war with Israel was in 1948, with the armistice signed in 1949; however, Israel has intervened in Lebanon against non-state military forces (e.g. the Palestinian Liberation Organization and Hezbollah) several times since then, most recently in 2006.
- Several other Arab states technically declared war on Israel and joined the Arab armistices, but never actually engaged in combat with the IDF. Most if not all of these countries have pledged to sign peace treaties with Israel upon the establishment of a Palestinian state, and some (including the Gulf States and Morocco) have good relations with Israel on the down low.
- Russia and Japan never did sign a peace treaty to end World War II, both claiming ownership of a handful of islands in the Northern Pacific, and neither willing to sign until the other drops their claim. They did, however, reestablish diplomatic ties and enter into a variety of bilateral agreements, so all issues usually handled via peace treaty have simply been handled in other ways, with the exception of the border dispute.
Treaties mean peace for now, not peace forever. The decision to accept or reject a treaty's conditions after or during the period in which it was in-force rests with the leadership of that day, and this decision is generally taken on simple risk-cost-benefit analysis. The oldest peace treaty containing conditions which are still honoured is that of the 1297 Treaty of Alcañices between the Kingdom of Portugal and Kingdom of Castile (later Castile-Leon, later Spain). Although the alliance fragmented in 1328 due to a marriage/succession dispute, the borders determined therein remain in use to this day.