Unsurprisingly, Lanchester's Square Law means that even marginally more numerous formations can have dramatically improved success and survival rates in combat - provided the co-ordination and/or combat-effectiveness of said more numerous formation(s) isn't so poor that their numbers can't make good on it. The larger group inflicts more casualties, which makes it even larger comparatively, which means it causes even more casualties compared to the enemy, and so on. Larger units can also back each other up with cover/suppression fire and assist in taking down targets faster, possibly even denying the enemy a chance to retaliate. Seriously, when you're already facing someone with a machine gun, chances are you're not gonna notice the second guy aiming for you, or the third or fourth. And if you do notice, you're probably going to panic and shoot badly. In use wherever possible by anyone who wants to win and/or take minimal casualties - i.e. everyone. The UK's armed forces, for instance, have a policy of never engaging their enemies in combat without at least 3:1 numerical superiority.
Although the Parachute Regiment fought a battle, uphill, in the dark, against enemies in fixed positions at 2:3 odds - and won - at Goose Green in the Falklands War, this was due to necessity and under-estimating Argentinian numbers. But if the Paras had known in advance, it probably wouldn't have fazed them anyway.
Another name for Zerg Rush is Human Wave Attack. It has historically been the traditional tactics of barbarian warbands and conscription armies who have masses of manpower but very little training.
Although with the advent of light machine guns, mines, and relatively accurate fire-support the human wave attack became obsolete (against Warsaw Pact and NATO forces, anyhow) by c.1960. Before then, the state of night-vision equipment and the co-ordination of fire-support was such that night-time 'human wave' tactics were actually a pretty good idea if you had a numerical advantage and/or were lacking fire support. This was the key to the People's Liberation Army's surprising effectiveness against UN forces in the Korean War despite their huge armoured-vehicle, artillery, and air-support handicap.
Unfortunately, human wave attacks have been known to be used in at least one case. A city in the Middle East was surrounded by a minefield. They got kids and young adults to clear it... by getting them drunk and having them sprint across the minefield.
The reason why Russia managed to win several battles against armies more organized than their own.
There's a Hungarian saying along the lines of "...as many as the Russians". Hungary lost both the revolutionary war in 1849 and the anti-Soviet rebellion in 1956 due to the enemy calling in Russian reinforcements, who employed this tactic.
In both cases it was a well-equipped and trained regular army against mostly Ragtag Bunch of Misfits rebels. There were no need to use human-wave tactics, so Hungarians' version of the story is probably just a feel-better tale.
In 1944 and 1956 this was certainly true, but in 1848/9 the Hungarian Republic possessed an uncannily strong and well-balanced regular army, and the Honved did actually manage to defeat the Habsburg armies arraigned against them and pushed them almost all the way to Vienna before the Russians came in from the East and the Habsburgs came in from the West and effectively squashed them flat.
Josef Stalin of course, applying We Have Reserves and the "Cannon Fodder" concept to the fullest extent in the first phases of the Great Patriotic War. When the Soviets got back on their feet, the Zerg rushes of 1941 and 1942 became much less common, instead relying on sophisticated maneuver attacks. After you lose 20 million men, there is not a whole lot of manpower to throw at the problem.
The use of Zerg rushes were mostly used in periods when an offensive was absolutely essential, but there simply weren't enough resources to adequately arm all the required soldiers. There were a few incidents where only the forward-most troops had guns, and those behind had to grab the guns from their fallen comrades when they got to them.note To enforce this, there were troops stationed at the back of the line to shoot deserters. As bad as WWII in Europe was for the Western Allies, it was nothing compared to how brutal it was on the Russian Front, hence WWII being known as "The Great Patriotic War." Norman Davies has suggested that a better term for the European theater of World War II would be Soviet-Third Reich War, because the scale of the Eastern Front absolutely dwarfs anything undertaken by the Western Allies, by several magnitudes, and the nations within the Eastern front were first obliterated during the war, then captured afterward, leading to the "East-West" European split. Your mileage may vary regarding the accuracy of the term.
During the latter stages of the war, the USSR abandoned the use of Zerg Rush infantry tactics, instead developing a robust combined arms doctrine that surpassed that of the Wehrmacht. The great infantry wave attacks of the early war were less doctrinal and more desperate attempts to stop the German advance into Russia. One area where the Soviets did remain wedded to zerg rushes was in the area of artillery, however: lacking the sophisticated communications and targeting equipment of the Western allies and the Germans, the Soviets made up for it with More Dakka.
The Japanese used Banzai charges to great effect in China during the Second Sino-Japanese war. They failed to note that this was because they were fighting against poorly-trained and ill-supplied Chinese soldiers (of the Guomindang, Guominjun, Guangxi Clique, and Yunnan) who had nothing but bolt-action rifles - for which each Chinese soldier was lucky to have even a literal handful of ammunitionnote Over the course of the war more and more Japanese weapons ended up in Chinese hands because ammunition production for their own weapons was just so inadequate (and the supply-chains so long or, in warlord troops' cases, virtually non-existent). Japanese helmets, combat-webbing, and shoes all became very popular as well, though this led to more and more friendly-fire incidents as the war dragged on. . They had no machine guns, mortars, artillery, or air support - and even the Guomindang had very little ammunition (relative to their troops' needs) for the few machine guns and mortars they did have. So when the IJA tried Banzai charges against American forces lavishly equipped with all of the above, and seemingly bottomless reserves of ammunition for them, their losses were devastating. It was made even worse by commanders issuing false reports on the efficacy of the tactic, resulting in the tactic being used again and again long after its uselessness had become apparent.
The Korean War had many examples of the Zerg Rush. North Korean forces would sometimes attack in massive waves usually with inadequate armament. One example being a human wave of people carrying nothing but baskets of grenades. Another being human waves of men armed only with submachine guns, charging over clear terrain from far outside their weapons effective range, against Americans armed with long-range rifles. These moments were still tense for the Americans, but they also found that the closer the Koreans and Chinese got, the more effective their rifles got, as their bullets would start going through their attackers, and continue on to hit another person in the wave. Important to note is that the Chinese military doctrine of a "short attack" was actually a combination of infiltration and shock tactics where fireteams would come as close to the enemy positions under any cover (typically night) and concentrate all their forces on specific breakthrough points where successive fireteams would be sent in to create a breach in the enemy positions and then the bulk of Chinese forces would move in the widen the breach. The attacks would be carefully timed to minimise casualties, however due to primitive communications fireteams would be sent in until either the Chinese ran out of ammunition a breach was finally opened up. This created a strong impression on the UN forces and resulted in the popular joke "How many hordes are there in a Chinese platoon?"
Other Wiki says "US Army historian Roy Edgar Appleman observed that the term "human wave" was a metaphor used by journalists and military officials to convey the idea that the American soldiers were assaulted by overwhelming numbers of enemies, but it had no relation to the real Chinese infantry tactics of the same period." Much the same is said of the Nazi German and subsequent NATO opinion of the (Soviet) Red Army's strategic manoeuvres and tactics, which were essentially (and dangerously, given their actual levels of post-war organisation and competence) dismissed as just what you'd expect of DirtyCommunists. That said, UN and Red Army records show several battles (Chosin, Spring Offensive, Hamburger Hill), wherein Chinese and North Korean forces were forced to make frontal assaults on UN forces with everything they had. This was hardly their favourite tactic (just as no-one at the Somme wanted to charge headfirst across no-man's-land into a sea of German MG rounds), but it was the best of a very bad series of options if they were caught out in the open (whilst preparing for more regular manoeuvres). While the Chinese were far savvier than most give them credit for, it's still hard to swallow the extent to which the Chinese leadership was willing to accept the sort of losses that came with their huge disadvantage in armour, air-power, and artillery.
There was once a military manoeuvre/unit known as the Forlorn Hope. These were the first men into a breached wall in a siege situation, so called because of their chances of surviving (also possibly a corruption of the Dutch for "Lost Company", Verloren Hoop). Anyone who did survive was automatically made an officer.
Among the French. While a British officer who survived the Forlorn Hope was promoted, for the men it was just the glory of having taken part and making it through.
A lieutenant became a captain and sergeants were promoted to ensigns. If anyone were to survive it'd be them...but it didn't happen very often...
And you had to lead it. Just being in it didn't guarantee promotion, one had to lead it from the front, and that person also carried the flag of his nation, showing everyone who to kill. See the Sharpe series for more info, as Bernard Cornwell gets it right.
During the American Civil War, the Union generals who typically won more battles were unafraid to lose massive amounts of men. In particular, several politicians rallied for Lincoln to fire Ulysses S. Grant due to the massive casualty rates of his soldiers. However, since Grant was one of the few generals Lincoln could count on to strike hard at the Confederates, Lincoln kept him on.
The Federals also had a higher population density then the Confederates. Thus Federal units could be recruited as needed, while Confederate units were mostly local military fraternities. The Federals also made extensive use of the Scorched Earth doctrine, using their quickly assembled units to smash Confederate economy and thus fulfill the RTS definition of a Zerg Rush (though it's worth noting that the South did plenty of the scorching themselves, to prevent supplies from falling into the North's hands). However, while the Union did suffer (roughly) 60% more casualties, the KIA excess was only 10%. Considering that the Confederates usually enjoyed the defending position (in the later years of the war, at any rate), and that the Civil War constituted the early days of trench warfare, with the known results during World War I, the numbers don't exactly point to rash tactics and disregard of one's own troops. Politicians lobbying against Grant had more to do with politicking after they decided the war was as good as won, using casualties as a pretext, than concern for the troops or about the general conduct of the war.
Bigger irony: while the casualties were terrible, the losses would almost certainly have been much lower if not for leaders trying hard not to get people killed or at least eager to avoid battle. McClellan essentially threw away the single most promising position of the war, with his troops in huge numbers and his guns available to pound Richmond and Johnson (later Lee). During Grant's campaign against Lee, he faced time and time again great advantages being ignored or lost by poor leadership at the Junior officer and even General officer level. The result was that the war was prolonged, eventually resulting in a shattered South and massive manpower losses - but also the complete destruction of slavery.
This is largely a myth that came about by Grant having the largest army in the war and fighting a lot of battles without stopping. He had a far lower casualty rate than RE Lee whenever you run the numbers Lee's casualty rate is somewhere between 19-23% depending on whose numbers you are using while Grant's is somewhere between 11-15%. Lee's bled the Army of Northern Virginia white with his overaggressive tactics.
It's also important to remember that throughout history right up until World War II more soldiers were lost to disease then battle. The longer the war drags on without resolution, the more soldiers you lose. Therefore, a zerg rush might wind up losing less men because it gets the battle over, rather than spending weeks fighting and losing more to disease.
World War I was particularly famous for the trench warfare of the Western Front, a fighting style which both sides were totally unaccustomed to. Throughout the war, hundreds of thousands of men died as both sides tried to repeatedly use mass wave attacks to achieve a "breakthrough" of the other side's defensive line, despite the fact of continued failure. Because both sides had created such a long trench line, neither could outflank the other, forcing attacks to be frontal assaults, which were made woefully ineffective with the introduction of the machine gun.
Made even worse by fact that there was no effective way to disrupt the enemy rail networks; so that even if a hole was punched through the first line of trenches the defender could rush troops to plug the gap faster than the attacker could reinforce their success.
Note that the Americans were accustomed to trench warfare on account of the Civil War experience, and placed emphasis on mobility once they got to Europe. Of course, by then the war was almost over.
In World War I, trench warfare itself wasn't the problem so much as evolutions in military technology. Traditional infantry and cavalry tactics against machine guns, poison gas and modern artillery was suicidal, as the opening month in France and Belgium showed. The Eastern Front between Germany/Austria and Russia featured more traditional, mobile campaigns yet accrued casualties comparable to (indeed, often in excess of) the Western Front. Traditional means of warfare weren't entirely obsolete, though. A cavalry charge in the First Battle of The Marne worked perhaps a little too well as a shock attack against the Germans as well as another cavalry charge in 1918 by the Canadians in the Battle of Moureil Wood, which was so successful against the entrenched machine-gunners that it entirely froze the Spring Offensive in its tracks, but at the same time cost the cavalry unit most of its horses and many of its men. And a few infantry bayonet charges in the Second Battle of Ypres in 1915 temporarily worked.
The importance of 'technology' is often vastly overstated. In particular, the chief cause of tactical failure in the first two years of operations on the western front in World War One was not machine guns... but artillery. More specifically it was the failure to allocate the artillery where it was needednote At the start of the war most artillery pieces were concentrated at a 'low' level. This meant that whenever artillery-support was most needed (i.e. during an operation/campaign), an awful lot of artillery wasn't being used for anything - because the units they were attached to weren't involved in the operation, their attached artillery wasn't involved either. At the end of the war, most artillery was at a 'high'(-ish) level. This meant that artillery was shifted wherever it was needed, and when an operation/campaign was happening there would be almost no artillery that wasn't used. , give the artillery the ammunition and spare parts it needednote Ammunition was a massive problem in 1914-15, as the combatants' industries still hadn't been fully mobilised and they'd all exhausted pretty much their entire pre-war artillery-ammo stocks in the first couple of months of the war. 'Spare parts', on the other hand, became a massive problem in 1916-18 when they started getting enough ammo for proper operataions/campaigns and they started using more of the artillery they had (as a result of concentrating more and more of their artillery assets at higher levels), and give the artilllery the information they needednote Concentrating more and more artillery at higher levels meant that more artillery was available for any given operation/campaign... but it also meant that there were more 'middlemen' and greater time-delays in communications between the artillery-observers (people at the 'front' [closest to enemy] of the battlefield who observe where the shells fall) and the artillerymen (people at the rear of the battlefield who fire the guns). This was particularly bad when it came to the direction-finding equipment used for identifying the location of enemy artillery (so you could fire upon it with your own artillery). Though this incredibly important tech was invented and mass-produced mid-war, because the direction-finding units were posted at so 'high' a level it wasn't until the very last year of the war that they managed to reduce the communications delays between them and the artillerymen enough that the equipment was actually useful - knowing full well that The Entente had such equipment, The Allies had taken to shifting their artillery about (firing just a few dozen shots, then moving the artillery pieces before firing again). When all these problems were solved, and the potential of artillery realised, The Entente were tactically unstoppable in 1918.
During World War II, the German military made effective use of this tactic, which they called the Blitzkrieg (Lightning War). When they invaded Poland, France, and Russia, they used fast moving vehicles to rush the enemy and bypass areas of strong resistance while simultaneously separating enemy army components, and using their air force to bomb critical enemy logistics and military structure. After disrupting the enemies rear lines and throwing them into chaos, the regular Army sweeps in and destroys pockets of resistance in piecemeal.
Russia made very poor use of this tactic in their invasion of Finland, where guerrilla tactics inflicted severe damage on the Red Army. In particular, their tanks subscribed heavily to this tactic, but in doing so, they were often exposed to unconventional weapons, like Molotov cocktails. Then the distinguished but incompetent in modern warfare Civil War Era generals were dismissed and replaced by the younger, more relevant leaders, the tactics were adjusted, and in two months the Red Army rolled Finns flat.note The war then ended with a negotiated settlement instead of the planned conquest of Finland, because of the threat of Britain and France joining the war on Finland's side. Which they actually were strongly considering. But this came at enormous cost; while Finland suffered 26,000 men killed in the war, the Soviets lost 127,000. One Red Army general is reputed to have said, "We have won just about enough ground to bury our dead."
In World War II tank combat, the US Sherman medium tank had mobility equal to the best German medium tank, the Panther, but inferior firepower and far inferior armor. The rule of thumb was that it would take four Shermans to match one Panther. Luckily for the Allies, they actually had more than eight Shermans to every Panther.
Similarly, the allied bombing campaigns against the Axis powers. In fact, bombing strategy of the time in general tended to center on massing enough aircraft to bullrush their way through the defenses to lay in their attacks, but this was most famously used by the heavy bombers of the US Army Air Forces and their daylight "Precision Bombing" campaigns in Europe. The effectiveness is much debating, however the German military was forced to disperse manpower and resources to provide air defense all across the continent, which they could have otherwise used in Africa, Italy, France, or Russia. Ultimately, the strategy worked because the Americans could build planes and train aircrew faster than the Germans could shoot them down, and the Americans got better at making it more difficult to shoot the bombers down, such as by extending the cruising range of the P-38 fighter (thereby allowing it to escort the bombers all the way to their targets)note A breakthrough Charles Lindberg achieved, by pulling back the prop control to 1200 RPM. They still paid dearly, however, and during the course of the war, the USAAF lost more men in battle than the entire US Marine Corps.
Not all is as it seems concerning this: While the Sherman was on paper a lesser tank than the Tiger and Panther, it was more a case of Boring, but Practical, not a Zerg Rush, as the loss ratio against the Panther comes out to 4:3 in the Sherman's favor. While numbers might have helped, it was not the decisive factor.
That would be Lanchester's Square Law in action. Tank numbers were never going to be a decisive factor - infantry anti-tank weapons, anti-tank and regular artillery, and air-support account for the vast majority of AFV kills throughout the war (and the Allied-German fronts were no exception). From the moment the Sherman-series first faced off against the Panther-series (later 1944), The Allies+Soviets had The Germans outnumbered by more than 5:1 in troops and 3:1 in AF Vs... and these numbers only increased in the not-Germans' favour.
Averted for the majority of all World War II combat featuring tanks. Being the clever little bastards they were, the Soviets figured that the best forces to use tanks against were the ones that couldn't fight back. Thus while Germany would happily use the same force for forcing breakthroughs and exploiting them, and The Allies were quite happy to simply use their vehicles and artillery to bludgeon their way through the enemy lines and grind them down with attrition, the Soviets did their very best to make their Zerg Rushes as unfair as possible by using as few tank formations as possible to make breakthroughs and massive Zerg-Rush-ey Mobile Forces containing all their armour to advance 100+km past them... and keep going. Ideally the exploitation-forces wouldn't meet a single German Panzer unit before they had to call a halt to the advance so logistics could catch up... and even if they did, why fight it when they could just go around it and encircle it too? The pride of Germany's Panzer forces, lost in the Ukraine in the Winter Campaigns of '43-'44, were not destroyed in tank-duels but were encircled and destroyed when trying to break out or simply abandoned by (fuel-less) crews fleeing on foot or surrendering. Ironically, the rivalry between Germany's regular and Panzer forces prevented them from ever realising the latter's vision of 'Blitzkrieg' - the latter insisted on encircling and reducing pockets of enemy forces themselves instead of focusing on advancing as far as possible, leaving Blitzkrieg's more ambitious cousin (Soviet 'Deep Battle' theory) room to shine.
In the fallout after Iran's 2009 presidential elections, this strategy was on the protesters' side. These riot police don't seem too confident. Any sizable riot going up against riot police is essentially this trope.
To what degree, if any, the police sympathize with rioters is a crucial element when considering a Zerg Rush against the government. The Iranian populace and the government have a "tense" relationship, and the economic sanctions levied against Iran for selling arms and developing a nuclear programme shattered the economy. The Internet, global news, and evolving international norms make it difficult for a government to order the slaughter of unarmed civilians without facing sanctions or complete isolation. Governments considered "illegitimate" by the majority of their people tend to become paranoid, but how long those regimes can hold power (both domestically and internationally) before such they slaughter or fall to a Zerg Rush is the open question. Since the mass murder of civilians usually prompts outcry and anotherZerg Rush, a sufficiently large protest tends to have the advantage.note Unless the nation's government is so ruthless it will slaughter civilians and the world community has no real power. China is Iran's foil in this respect: the Chinese economy is, well, "too big to fail," so the international community's hands are tied, unless a land war in Asia sounds like a good idea to you.
During many of the Communist collapses of the late 80's (Romania is particularly notable for this effect), the regime collapsed precisely because the military ultimately refused to slaughter the rebelling populace (largely because they no longer believed in the regime). Some say the 1989 Tiananmen (Gate of Heavenly Peace) Square and related protests were heading this way, when troops from the local (Zhili) military district were brought in to get people to disperse. However, as they spoke the same dialect/language and came from the same area, very few were willing to use force to get the striking workers and student protestors to go back to work or to their studies, respectively. The Party had to get the local forces to stand down and then bring in divisions from another military district, briefing them that the city had descended into foreign-orchestrated riots and anarchy, before ordering them to disperse them by force. Maximum force, in some cases, though the numbers are disputed and there is really no way to be sure without access to the CCP's archives. Something similar happened in the USSR too, but there (unlike Romania, which was led by a real autocrat) even the leadership itself was reluctant to use force, and calling for the army was more of a kneejerk reaction rather that the real intent, so everything just kinda petered out.
The same business occurred in the Arab Revolutions of 2011; the governments of Tunisia and Egypt fell more or less because their militaries refused to fire on protesters, and other techniques were useless because of the sheer number of protesters. Libya turned into a Civil War and Syria and Bahrain turned into bloodbaths because the government forces were willing to fire on the people; however, we should note that because the Libyan and Syrian militaries/security forces had similar demographics to the general public, defections to the protesting side kept the situation protracted, while the fact that the Bahraini forces (and the Saudi and Emirati forces they called in to help) were primarily Sunni and the protesters primarily Shia made defections less of an issue, and the uprising was crushed as a result. On the other hand, ever-Genre Savvy Morocco explicitly ordered its security forces not to fire on protesters no matter what they did, which is why the protests there never got that big and why the regime was able to get away with moderate reforms.
The USSR is an odd case of a nation collapsing peacefully, something that hasn't happened since the advent of the nation-state system. The most westward of the SSRsnote Soviet Socialist Republics — Estonia, Latvia, and Lithuania ("The Baltics") — were already under the doctrine of "Baltic exceptionalism," so when protests began, an armed response was off the table. (The Baltics have historically been considered part of Europe, which was why the Soviet government opted against crushing the rebellion; the odds that the conflict would escalate and turn into a proxy war were far higher. Gorbachev was also in the middle of instituting a number of reforms and caught up in an intra-party war for power, and it's unlikely his worldview would have allowed for armed response (i.e., massive civilian causalities), so the Baltics were the first out.)
The Soviet government was the victim of a Zerg Rush itself, led by the president of Soviet Russia — Boris Yeltsin, who stood atop a tank in Red Square demanding sovereignty for all Soviet nations. It could be argued that the government in Russia only changes byZerg Rush — it was a major tactic of the Bolsheviks, of the pro-democracy movements that ended Soviet rule, and, as of The New Tens, it's the new fear. Vladimir Putin faced protests after his third election to the presidency, the major slogan of which was "Russia without Putin," so the state issued a cap on the number of protestors allowed. It's impossible to know what the effect would have been had protestors not been scared away, but they were the largest protests seen since 1991.
European warfare in the 18th century, after the devastation of 16th and 17th century total wars, had become a sort of song and dance with opposing generals actually meeting each other to mutually minimize their casualties, and to avoid destroying the actual resource they were fighting over. This style of warfare is actually exactly the method which Sun Tzu's "At of War" sees as the most efficient - to win the enemy by manouevre, and attacking his plans and alliances instead of his forces. The rule of warfare was to wear brightly colored uniforms so that everyone knew just who was on whose side, and to use thin files so one row at a time could fire, then get out of the way while they reloaded. This was not a very effective way to win (or rather kill), but was (relatively) predictable, respectable (in context), and (relatively) civilized; it was generally agreed to because highly disciplined, professional soldiers in this form of warfare were expensive to train, keep, and equip. In a case of victory, it also usually provided better outcomes of war than outright carnage and devastation. This system ended with the French Revolution; suddenly you have a French army five times its pre-Revolution size, much less trained as a whole, aggressive as a hornet's nest and directed by a government more encroaching on the general populace than the kings could ever manage and under attack by most of its neighbors (and then going on for the counter-attack), with generals who had none of these dainty sensibilities and qualms about where replacements for killed soldiers were going to come from or what the upper crust in snooty aristocratically-run nations would think...
Highland Charges in the 17th and 18th century. Unlike what happened in Braveheart, traditional Scottish tactics called for tight and disciplined blocks of infantry. When newer firearms made those tactics obsolete they switched to a screaming charge at the enemy line, which was extremely successful when their enemies would break ranks. When other armies started training their armies to defend against them, they got massacred.
Other factors, such as improved firearm drill, the invention of the bayonet and canister shot, also made the strategy obsolete.
The Spanish Civil War degenerated into this quite a bit, most infamously at the Ebro river, which mixed WWI trench warfare with RCW/WWII Eastern Front political persecution. Results were tragic but predictable.
Reportedly used by the passengers on United 93 to defeat the hijackers.
As a general rule the Zerg Rush does not work against a well-fortified position and concentrated fire. See Zulu Wars; Pickett's Charge; WW I...
Though in the case of the Zulu, the Rush (in a slightly more complex form) was in fact a fairly new and effective tactic by which the Zulu had come to dominate the region, the work of a military genius who was unfortunately dead by the time the Zulu met the British. Had someone like him been around at the time, the Zulu might've fared better, as shown on one occasion when they did manage to get hold of some artillery.
In the FAT32 filesystem, each file occupies a minimum of 16KB of disk space, even if its size in bytes is less than that. Thus, tons of tiny files can waste much more disk space than a few big files.
This actually depends on how the filesystem was setup. File systems addresses space in terms of clusters, in the case of FAT32, 2^32-1 clusters. However, you can set cluster sizes to 64KB, meaning, at the minimum, all files will take up 64KB.
Similarly, Google Chrome. Unlike other browsers, each tab is its own process (basically, each tab is run as it's own program). While this has benefits such as a small number of tabs running better and crash resistance (one tab crapping out won't cause others to), it also means that having a large number of tabs can end up taking up a disproportionately large amount of memory, even if all those tabs are simply blank pages.
In Humans Versus Zombies, this is the only reliable way to take down a good player. Against guys who have real world combat experiencea, anything less than six or so zombies, is not going to do them in.
The internet. Want to get quick results when someone stole your artwork? Got a conflict issue that you want to spread out quick and get support? Post somewhere prolific, with substantial proof. Now sit back and watch as the Internet Zerg Rushes someone's mailbox/account...
A Zerg Rush is the core element of less organized, 'invasion'-style denial-of-service attacks: If you can ram enough people's packet requests into a system, it can't dispatch answers fast enough and crashes.
Particularly nasty hackers not only launch denial-of-service attacks on a site they want to shut down, they'll hijack your computer to do it for them.
Non intentional use: Could you imagine this tactic with fangirls yelling and going Squee out of the blue? Well, this was actually the reason why The Beatles stopped giving concerts in 1966...
Hunter-gatherer societies tend to have taboos against having many children. Agrarian societies encourage large families. (Think about the ideal Chinese family, pre-Deng: Three boys and three girls.) Obviously, the agrarian societies won.
This has nothing to do with combat, though. Hunter-gatherer societies tended to have fewer kids because their food source was unreliable; ergo, you wanted a minimum of mouths to feed because you never knew how much food you were going to have. Agrarian societies, on the other hand, have a steady, reliable food source, so the focus is on having enough hands to cultivate the food.
Of course, this only works for a time - now it's back to the "1-3 children per family" mindset once civilizations move past the Industrial era.
Also consider that almost all hunter-gatherer societies are nomadic. As mothers have to carry babies and small children, they couldn't have too many children, while settled people could have as many children as they could feed.
Unix makes spawning processes trivially easy. A malicious user can easily create a fork bomb, a program that reproduces itself until it eats up all the process table entries.
You wouldn't think that this would be possible in sports, given the way that teams are normally balanced. Well, China has other ideas about that. Real Madrid football (soccer) club has played a game against a team made up of 109 Chinese children.
Soldiers of the Japanese 3rd Army in the battle and siege of Port Arthur during the Russo-Japanese War. Japanese soldiers hurled themselves against stout fortress defenses, dying by the thousand.
Averted. Those charges did absolutely nothing, with thousands of men dying for no ground gained... until the commanders of the infantry and artillery finally agreed to work together, extremely closely, with the artillery deigning to give the infantry prelimary bombardments for their attacks and fire-support on-demand once they were underway. The reality of Japanese victory at Port Arthur was nowhere near as cool or interesting as the Zerg Rush thing, though, so guess which story everybody (including the Japanese themselves) heard about courtesy of the war-correspondents there to witness the fighting?
Famously subverted at the Battle of Thermopylae, which funneled the massive zerg rushing Persian army into a narrow corridor straight into Greek spears. Numbers counted for nothing.
Many spambots and other botnets try to create forum posts faster than the mod/admin personnel can delete them.
Picornavirus germs. Usually for a germ it is not a good idea to kill your host, since it will also mean your own demise. Picornaviruses avert this fate by simply breeding in gazillions: they are highly contagious and their strategy is to multiply so much that it really does not matter if your host will die or not in the process. Diseases which these nasty germs cause are influenza, poliomyelitis, hepatitis, cattle hoof-and-mouth disease etc.
Ants do this. It's called Marabunta. Everything is wasted. They are probably the inspiration from which human wave attacks are drawn.
Ant-termite wars are the epitome of this trope, as endless numbers of ants charge matching waves of termites. Every bit as epic as human battles, and casualties are predictably enormous.
Driver ants (the siafu) use similar tactics for downing prey and are capable of blanketing a forest floor for miles around their nest. They even apply zerg rushes to physical obstacles, when they encounter an impassable barrier they use themselves as ramps.
Even a fight ants vs. ants gets zergrushed. The Argentian ant, much smaller than the indigenous species, invades Europe. See The Other Wiki
The army ants of South America take the zerg rush concept to its logical extreme. While the ants normally feed using mass foraging, when they enter their nomadic phase the entire colony will move as one to a new home consuming any prey unlucky enough to be in their way.
This defensemechanism employed by Japanese honeybees against a particular type of hornet. Interestingly enough, it's not your typical "sting it 'til it dies" tactic you would expect from a hive of bees, because said hornets can apparently take it. Instead, these bees pile on top of the hornet and roast it alive by vibrating, their own tolerance for heat just barely higher than that of the hornet's. European and, presumably, African honeybees have lower tolerance for heat and so they cannot employ this tactic.
Science Marches On back the way it came, however! There's at least one fossil trackway evidently made by deinonychosaurs that clearly demonstrates cooperative travelling, which means that the theory of pack-hunting raptors is still plausible. This article explains it all.
Non-malicious example: baby sea turtles are laid in huge clutches, so that when they hatch they overwhelm their predators with turtles, in the hopes that a few will get through to survive.
Sea turtles aren't the only ones. Cicadas emerge in huge numbers to overwhelm their predators, and plenty of the noisemakers escape to breed. Predator Saturation is prey species' version of a Zerg Rush.