The Neutral Zone

And these are the guys who shot down Germans and Americans, and then received apologies afterwards.

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.

The flip side of this is the Truce Zone, where opposing sides are encouraged to come in and mingle as long as they behave.

Not to be confused with The Friend Zone.

Examples of The Neutral Zone include:

Literature

• 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.

Live Action TV

• 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 they 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)
• The re-imagined Battlestar Galactica Reimagined 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.

Video Games

• In Mass Effect 2, Planet Tuchanka (the krogan homeworld) is in a sector known as the Krogan DMZ.
  • Although in this case, it's only restricted to keep the krogan contained, and to keep stuff the krogan can steal away from them.
  • 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.

Western Animation

• 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.

Real Life

• 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 most states had large areas over which control was dubious.
• The Demilitarized Zone between North Korea and South Korea, 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 has been overrun by wild plants and animals, including several threatened and endangered species (such as the Red Crane and the Amur Leopard, the latter of which is critically endangered).
  • The Vietnamese Demilitarized Zone, established after the French left as a result of the First Indochina War, was eventually utterly ignored by the North Vietnamese during the Vietnam War.
• 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 occupied the Rhineland in protest at tardy German repayment of reparations.