Saavik: I'm aware of my responsibilities, mister.
The Neutral Zone is a place between two opposing territories where nobody from either territory may go. (Or at least nobody with weapons.) It's frequently found in Speculative Fiction, primarily Space Opera and Wagon Train to the Stars.
The mere mention of the Neutral Zone by any Captain immediately prompts a Bridge Bunny to remind us that for any starship from either The Federation or The Empire to enter it is considered an act of war. Naturally, there will be some tempting reason to enter the Zone anyway. Planets in or near the Neutral Zone are frequently disputed territories, and are often sources of Applied Phlebotinum.
In space settings, it is rarely if ever explained exactly how a Neutral Zone would be enforced, given that the huge distances and 3D nature of space mean it's not a simple as "put checkpoints at these mountain passes and make sure everyone has the right passports".
The flip side of this is the Truce Zone, where opposing sides are encouraged to come in and mingle as long as they behave.
- In the novel Succession (published in the UK as The Risen Empire), there's an area called the Plague Axis where medicine is avoided so that the people will build up natural immunity to various pathogens. This area contains representatives from the four main galactic powers, and is not considered to be affiliated with any of them. Entering it isn't exactly an act of war, though it will make the other powers suspicious.
- The Kris Longknife series has the No Go Zone between human space (originally the Society of Humanity, which is dissolved at the end of book one) and the Iteeche Empire. This was established by a treaty that ended a bloody border war eighty years before the start of the series, and neither side is allowed to cross it lest the other destroy their ship on sight. In Undaunted, an Iteeche ship seeking to open diplomatic relations crosses it and makes contact with Kris.
- Star Trek had three neutral zones, separating each of the three primary powers from one another: The United Federation of Planets, the Romulan Star Empire and the Klingon Empire (after the events of the sixth film, the neutral zone between the Federation and the Klingons no longer exists, as the two governments entered into an alliance instead of being enemies). Generally, "The Neutral Zone" refers to the Zone between the United Federation of Planets and Romulan Star Empire, otherwise called the Romulan Neutral Zone, as it was the first and longest lasting Neutral Zone. The Planet of Galactic Peace was where the borders of all three powers meet. Though not quite as exclusive as a Neutral Zone, the Demilitarized Zone between the United Federation of Planets and the Cardassian Union has many of the same features, but does allow some travel, communication and settlement for various reasons. Military vessels are prohibited unless a joint operation can be arranged, as is either party arming their colonists (not that such regulations stopped either group of colonists from arming themselves). Ironically, quite a few episodes that involved the Romulans started with one of the two factions - or both - illegally entering the Zone for some reason.
- Battlestar Galactica has (had) the Armistice Line.
- There are also the Uncharted Territories from Farscape, part of which acts as a buffer between the Scarrans and the Sebacean Peacekeepers, while the rest is simply the vast unknown beyond the parts of space that have been explored and mapped by either major power.
- The Man in the High Castle: North America is divided between a Nazi German puppet state in the east and an Imperial Japanese puppet state in the west. The large swath of area in between centered on the Rocky Mountains is a demilitarized zone unclaimed by either of the Axis states. As such there is no overt totalitarian oppression or racial policies, but at the cost of pretty much being a lawless hellhole instead, with decades-old infrastructure decaying and Wild West-style justice.
- In Madam Secretary, US intervention in the civil war in Ukraine culminates in the Air Force enforcing a no-fly zone over the eastern part of the country. This leads to a Curb-Stomp Battle with the Russian Air Force after fighters supporting the pro-Russian rebels cross the border into Ukraine.
- Negotiating these is common as part of an alliance. Their advantage is that it guarantees the alliance because no one can advance their troops far enough to hurt the other without being noticed. The disadvantage is that everyone else will know they are allied. One of the more interesting snarls analyzed by Diplomacy fanatics is the Italian/Austrian border (specifically, Venice and Trieste), the only case where two players' home supply centers border each other. On that one, each player has a military unit right next to a rival supply center; if a neutral zone agreement made at the beginning of the game is betrayed, that could permanently cripple one player and start the other with a great advantage.
- A negotiated "bounce" (two powers agree to send units of equal strength to a given territory - assuming nothing else interferes both units are sent back to their previous position) can be thought of as a downplayed version of the above, since the end result is that the territory in question still remains unoccupied (assuming no one's there to start with). On one hand, a bounce is easier to arrange to its intended conclusion since both sides know if they do something else with that unit the other side will take the territory unopposed; on the other hand, this ties up units that could be doing other, potentially more beneficial things like attacking other supply centers.
- More directly, Switzerland is outright stated in the rules as being impassible by any unit. Implicitly by not being labelled, all islands on the map save for Great Britain are also impassible.
- These are common in strategic board games based on history. In Axis And Allies for instance, Switzerland, Turkey and Spain are neutral as they were during World War 2. Depending on the game, moving through a neutral territory may be outright impossible, or penalized for violating it (e.g. all other neutral countries joining your enemies).
- Traveller: there is mention of an Imperial/Zhodani DMZ in the volume Behind the Claw. Details are not given.
- In Fen Quest, the Northern and Southern empires are separated by Shroomleaf Forest, inhabited by barbarian tribes. Since both empires are mostly in a cold war by now, they both leave the forest relatively untouched, only occasionally conscripting some barbarians for military or farm work.
- In Mass Effect 2, Planet Tuchanka (the krogan homeworld) is in a sector known as the Krogan DMZ. That being said, while Tuchanka is free to remain a battlefield between the warring factions, the restrictions are in place to prevent the mobilisation of a standing army and Space Navy that might threaten Citadel Space.
- May also apply to the buffer between Citadel Space and the Terminus Systems. Any incursion from an armed force greater than say, a Spectre, is seen as an act of aggression and is likely to trigger a very strong response that may even lead to war. This is despite the fact that aside from Aria T'Loak on Omega, there is no unified leader or government amongst the various disparate factions that operate within the Terminus Systems.
- Until the events of the first game, the Perseus Veil unofficially served as this between the rest of the galaxy and Geth-controlled space.
- In Chaotic, the Doors of the Deepmines was a location were the tribes of Perim were forbidden to engage in combat even though all four are currently at war. This was probably to prevent any damage to the the location that acts as the prison containing M'arrillian tribe.
- Switzerland's neutrality has gone to a point that jokes about it have become cliché.
- For a few years after Operation Desert Storm and the first Gulf War in the 1990s, portions of Iraq were a "no fly zone" for Iraqi aircraft. This area was named by the UN as "The Neutral Zone."
- Saudi Arabia once had neutral zones with both Iraq and Kuwait. Rather than the buffer zones as seen in Star Trek, they were simply areas where the exact location of the border hadn't been determined. Both ceased to exist when the border disputes were settled. 1970 for the Saudi-Kuwaiti neutral zone and 1981 for the Saudi-Iraqi neutral zone, though for unknown reasons in the latter case no one outside of Saudi Arabia and Iraq was informed of the treaty for another 10 years. As a result, maps made prior to 1991 depicted a neutral zone that did not actually exist.
- That used to be fairly common in the Middle East and North Africa, and most states had large areas over which control was dubious. In fact, even now that the borders are settled, control is still dubious—the borders are only controlled around the transportation links. There tend not to be fences along more than a few miles of border, and as for the rest, gigantic deserts serve as a decent substitute for border control (you try crossing the Sahara or the Empty Quarter without passing too close to a major route or dying). The main exception is Israel's borders, where the desert is small enough not to be a deterrent.
- Demilitarized zones put in place between two hostile powers are a way to enforce nascent ceasefires and armistices. Some examples throughout history:
- The Demilitarized Zone between North Korea and South Korea, probably the most well-known in the modern world. In business since 1953 (though it's demilitarized In-Name-Only [read: it's full of land mines] to remain neutral). Sailors and members of the other branches of the armed forces stationed in South Korea are repeatedly warned that if one decides to enter the Korean DMZ, he or she is no longer under the protection of their home nation. They are on their own, which is why entering the DMZ in the first place is strongly discouraged. An unintended positive side effect of this is that the whole Korean DMZ has been more or less untouched by humans for over fifty years, and as a result is basically a de facto nature reserve, having been overrun by wild plants and animals, including several threatened and endangered species (such as the Red-crowned Crane and the Amur Leopard, the latter of which is critically endangered). In fact, several bird species are likely to go extinct if peace is ever restored (unless the relevant parts of the DMZ are turned into a de jure nature reserve, an idea that has been floated).
- The Vietnamese Demilitarized Zone, established after the French left as a result of the First Indochina War to separate the communist North from the noncommunist South, was eventually utterly ignored by the North Vietnamese during The Vietnam War.
- The Berlin Wall's "death strip". There were actually two barriers put up in the early 1960's, one just inside the East German side of the Inner German Border and the other about 100 meters further into East German territory - the former is the one that got graffiti all over it since legally the West Berlin police could do nothing about stopping it even if they wanted to. In between, the land was strewn with land mines and raked so that footprints could easily be detected by East German guards, who had standing "Schießbefehl" ("order to fire" - one verbal warning, then a warning shot, then shoot to kill) at anyone attempting to flee to the West.
- There was a demilitarized zone in the Rhineland of western Germany between World War I and Hitler's taking over of it in 1936.
- Although this wasn't the first time it had been taken over. In 1924 the French and Belgians occupied the Rhineland in protest at tardy German repayment of reparations.
- In medieval Europe, a "march" or "mark" was a territorial borderland that served as a buffer between rival kingdoms or other entities; the word lives on in modern times in, among others, the country of Denmark.
- Buffer states can serve as neutral zones between two larger powers in order to forestall conflict between them. How successful the states in question serve as neutral zones to the big powers on either side of it largely depends on how much its leaders can play the rivals off one another without falling squarely into one side's camp.
- In American Football, the neutral zone is the strip of field running from sideline to sideline marked by where each end of the football is located after the referee spots it. No player except the center is allowed inside this area before the ball is snapped - if a player lines up in the neutral zone (or beyond) when the ball is snapped, it's a five-yard offside penalty on the offending team (the play, however, will be allowed to continue to its normal completion - the offended team will then have the option of taking either the play's result or the penalty).
- A "neutral zone infraction" is called if a defensive player jumps into this area (or beyond) and causes an offensive player to react to the big guy suddenly charging towards him - the play is blown dead and a five-yard penalty on the defense is assessed (unlike an offside penalty, the penalty will always be enforced as there was no play at all).note