In later stages of the game, tactics will become increasingly important, and diplomacy increasingly unimportant. In the early game, players often have to cooperate in order to get anywhere, but in the late game, one or more players will be so powerful that they can handle wars against their neighbours without any outside help.
The Grand Alliance is a coalition formed to stop a power from achieving a solo victory. This will occur once one power has around fourteen or fifteen supply centers. Minor powers, left with one or two supply centers, will bandwagon with whoever is the second strongest power to exterminate the strongest to survive and rank 3rd or 4th.