The rules are very different from what you would expect, since it is a diplomacy game and not a war game. From Wikipedia:
Diplomacy is turn-based — the game begins in the year 1901, with each year divided into two turns: "Spring" and "Fall" turns. Each turn is further divided into negotiation and movement phases, followed by an end-of-year phase after the Fall turn.
In the negotiation phase, players use any verbal means necessary amongst each other to form alliances, or some other form of arrangement, with one another. Such arrangements may be made public knowledge or kept secret. Since players are not bound to anything they say during this period, and thus no agreements of any sort are enforceable, communication and trust are unusually important for a strategy game; players must forge alliances with opponents and observe them to ensure their trustworthiness; at the same time, they must convince others of their own trustworthiness while making plans to turn on their allies when others least expect it.
After the negotiation period, players write secret orders for each unit; these orders are revealed and executed simultaneously. Units can move from their location to an adjacent space, support adjacent units in holding an area in the event of an attack, do nothing or assist in attacking an occupied area. In addition, fleets may transport armies from one coast square to another. One fleet per sea space traversed is required if multiple bodies of water are to be traversed. Armies may only occupy land regions, and fleets may only occupy sea regions and land regions that border the sea. Only one unit may occupy a square; if multiple units are ordered to move to the same square, only the unit with the most support moves there (if two or more units have the same highest support, no units ordered to that square move).
During an attack, the greatest concentration of force is always victorious; if the forces are equal a standoff results and the units remain in their original positions. If a supporting unit is attacked (except by the unit against which the support is directed), its support is nullified, which allows units to affect the outcome of conflicts in regions not directly adjacent.
After each winter move, newly-acquired supply centers become owned by the occupying player, and each power's supply center total is recalculated; players with fewer supply centers than units on the board must disband units, while players with more supply centers than units on the board are entitled to build units in their Home centers (supply centers controlled at the start of the game). Players controlling no supply centers are eliminated from the game, and if a player controls 18 of the 34 supply centers, that person is declared the winner. Players may also agree to a draw.
The game can be found at http://www.gamesbyemail.com just like A&A. Who's in? It supports up to 7 players so everyone can play in one game, and it allows you to force moves for those times when people disappear for days on end.