• Austria-Hungary starts with an army in Trieste instead of a fleet. The Imperial and Royal Army was the glue that held the Empire together. The undernourished Austro-Hungarian Navy was little more than an afterthought. This third army greatly enhances the Dual Monarchy's flexibility and options.
• Britain starts with four units: F London, F Edinburgh, F Gibraltar, and F Egypt. Note that Liverpool is still an SC, but the army that starts there in Diplomacy is gone. At the same time, note that Gibraltar is not an SC. Britain was the premier sea power at the turn of the century, but its puny army was almost embarrassing for a nation of Britain's stature. The vaunted, and diminutive, British Expeditionary Force wasn't formed until just before WWI.
• France starts with four units: A Paris, F Brest, A Marseilles, and A Algeria. The last unit reflects the military presence France maintained in its African territories. The strong French garrison was no doubt a prudent deterrent given Italian ambitions to establish an African empire that the Romans themselves would have been proud of.
• Germany starts with four units: A Berlin, A Cologne, F Kiel, and A Munich. The supremacy of the German army was acknowledged, grudgingly, by all of the Great Powers. In standard Diplomacy, however, Germany seems pathetically weak when compared to the actual colossus that was the Second Reich. The additional army gives the Kaiser real options to conduct a two-front war if necessary or desired.
• The Italian army that started in Venice now starts in Milan.
• The Turkish army that started in Smyrna now starts in Damascus.

With the few exceptions discussed below, all rules for Diplomacy apply to 1900 as well. In all but two cases, the rule changes represent little more than minor revisions to account for the new map. The two major exceptions are the Suez Canal Rules and the Russian Emergency Measures (REM) Rule. The Suez Canal Rules are a series of rules governing movement and combat between the Mid-Atlantic Ocean space and the Egypt/Hejaz spaces. These rules serve to give 1900 a distinct character primarily because they dramatically increase the need for all of the Great Powers to talk to each other from the beginning of the game, an end state the variant creator definitely hoped to achieve. The Russian Emergency Measures Rule was a late addition to the variant rules that was felt necessary to enhance play balance. This rule's purpose is to boost Russia's defensive prospects after repeated game play showed that Russia was not achieving the results that had been anticipated.

The minor rule changes go as follows:

• Victory conditions have not changed. If a Great Power gains control of eighteen supply centers, the game ends and the player controlling that Great Power is declared the winner. With thirty-nine supply centers, though, it is now possible for two Great Powers to get eighteen supply centers on the same game-turn. Should this happen, the player representing the Great Power with the most supply centers is the winner. If the two Great Powers each control the same number of supply centers, play continues until one Great Power controls at least eighteen supply centers and that Great Power controls more supply centers than any other Great Power.
• Egypt and Algeria, while controlled by Britain and France respectively at game-start, are not considered home supply centers. This means that Britain may not build in Egypt and France may not build in Algeria. This also explains why Egypt is not called Cairo and Algeria not called Algiers.

The Suez Canal Rules go like this:

• A fleet may move back and forth between Egypt and Hejaz.
• Movement between Egypt or Hejaz and the Mid-Atlantic Ocean is allowed. It is assumed the unit travels around the southern tip of Africa. A unit that moves in this manner does so at half strength. This means that a unit adjacent to Egypt or Hejaz succeeds in moving there if opposed only by a fleet moving from the Mid-Atlantic Ocean and a fleet adjacent to the Mid-Atlantic Ocean succeeds in moving there if opposed only by a fleet moving from Egypt or Hejaz.
• A fleet in Egypt or Hejaz cannot support a unit holding in or moving to the Mid-Atlantic Ocean. This is true even though the fleet in Egypt or Hejaz can itself move to the Mid-Atlantic Ocean. Likewise, a fleet in the Mid-Atlantic Ocean cannot support a unit holding in or moving to Egypt or Hejaz.
• A fleet moving from Egypt or Hejaz to the Mid-Atlantic Ocean does not cut support being provided by a fleet already in the Mid-Atlantic Ocean unless the attack results in F Mid-Atlantic Ocean being dislodged. The opposite is equally true. A fleet moving from the Mid-Atlantic Ocean to Egypt or Hejaz does not cut support being provided by a unit already in Egypt or Hejaz unless the attack results in the unit being dislodged.
• F Mid-Atlantic Ocean can convoy an army from or to Egypt or Hejaz. An army convoyed from Egypt or Hejaz attacks its destination space at full strength. An army convoyed to Egypt or Hejaz attacks at half strength.
• If two units are retreating to Egypt or Hejaz, or the Mid-Atlantic Ocean, and one of them must travel around the southern tip of Africa, the unit that does not travel around southern Africa may retreat while the other unit is disbanded.

The Russian Emergency Measures Rule goes like this:

Russia's greatest military assets at the dawn of the 20th century were its seemingly endless supply of manpower and its vast resources. Unfortunately, terrible mismanagement and a weak economy prevented Russia from successfully exploiting these assets. If Russia were to suffer a severe setback, such as is implied by the loss of a home supply center, it seems reasonable to assume the Russian government would be shocked into taking drastic measures to overcome the situation, to include stripping the many garrisons stationed throughout the Asiatic portions of the Empire and better managing its limited industrial capability. In game terms, this is done as follows:

• Whenever Russia possesses at least one, but not all four, of its original home supply centers, it is entitled to maintain one extra unit on the map (i.e., one more than the number of supply centers it currently controls). Additionally, while Russia is in this condition, the Russian player may use Siberia as a build site during the adjustment phase, if Siberia is unoccupied.
• Should Russia fail to possess at least one home supply center or should it regain possession of all four of its home supply centers, the ability to maintain an extra unit is lost and any excess units must be disbanded during the subsequent adjustment phase. Further, Siberia reverts to its normal status (that is, it is no longer a build site).
• Note that Siberia, while it may become a build site, never attains supply center status.

A Gamers' Guide to 1900 (PDF format) is also available to help players understand the variant.

Baron Powell, the creator of 1900, wishes players to feel free to contact him at VonPowell@aol.com.