Civilization V: The Celtic Chronicle, part 1 (4000 B.C. to 1150 B.C.)
2925 B.C.: Seemingly unaware of the secret Celtic-Russian Alliance, the French chieftain approaches the Celts asking for aid against Russia. The Celtic cheiftain responds, "Well, um uh... we were just about to eat dinner, so... maybe next time?"
Interesting position here. I basically have the same amount to gain by joining either side, so the outcome of this war falls solely to my somewhat arbitrary decision. I decided, for the sake of honor, to hold to my original agreement with Russia. This will make the French suspicious, but there's not likely to be much they can do about it.
2900 B.C.: A long conflict between the Celtic-Russian Alliance and the French tribes begins when Celtic forces engage a French warband near the source of the River Celtica. The Celtic warriors settle in, knowing this will be the first test of their mettle against a foe greater than mere roving barbarians.
2850 B.C.: The Germans request a public declaration of friendship with the Celts, which they quickly accept. The beginnings of a three-way league of Celts, Russians, and Germans take shape.
A Declaration of Friendship isn't as good as an alliance, but it means Germany will be a lot less likely to attack me or help my enemies. If I can keep close bonds to them as well as the Russians, France and England don't stand a chance. We may have this whole subcontinent to ourselves by the mid-game.