From my understanding of the language and the concept, I believe that go no sen is 後の戦, sen no sen is 先の戦, and sensen no sen is 先々の戦. The first, go no sen, meaning "post-war", the second, sen no sen, meaning "battle ahead", and the third, sensen no sen, meaning "battle of the distant future." One of my friends described sensen no sen as taking action when you see intent, sen no sen as as the attack begins/ at the same time as the attack, and go no sen as after the attack has begun.