Diplomacy (1999) чит-файл №1

Hint: Never start a two-front war. For example, when playing Germany, ally with
either France or Russia while you attack the other; you'll never accumulate
enough resources to support an attack on both.

Hint: Master the concept of "support." Live it, breathe it. In a game that only
allows one unit per territory and in which all units are equal, knowing how
and when to support your attacks is critical for military success.
                               
Hint: Learn the AI. Often, the AI will begin the game with the same moves:
France moves west, Austria-Hungary south, and so on. Learning the computer's
tendencies can make your life much easier. For example, form an alliance with
France on the first turn. Let the French move on Spain and then attack their
undefended eastern borders in the second turn.