In an international war, the player must take risks from time to time to gain great victories. In order to know which risks to take, always think ahead 1 turn. This lets the strategist observe what the enemy's probable action will be in reaction to the present move he is making, and counter it in advance. This gives the strategist tempo, an unbreakable lead in every movement. It forces the enemy to fight a losing battle which will ultimately lead to invasion.
One must remember to make friends with a timid and honest person who, no matter what they plan, never succeed in following through. They must also make sure to tip the balance in their favor only on 1 front at a time. Total victory everywhere at once, while attractive, leads to isolation and betrayal.
There is always a dominant country in any alliance. One must be dominant in order to win and to deter allies from betrayal. If necessary, ally with weak and incompetent leaders when possible, or become self-reliant rather than lean on an ally with a mind of their own and a desire for domination.