Civilization V: The Celtic Chronicle, part 2 (1150 B.C. to 520 A.D.)

T.J. Hafer at

Unexpected allies

475 B.C.: With Pictish Warriors already on the march toward England, the Swedes send a messenger proposing a joint war against the English. Long having resisted friendship to preserve relations with Germany, the Celts are nonetheless overjoyed by this proposal. They assure the Swedes that their men will be welcome friends on the battlefield.
All hail the holy PC! It is truly a miracle! A slightly fish-scented, Swedish miracle! Assuming they don't pull a Russia and back out when my forces are already committed, this is terrific news.

France and Germany make a public declaration of friendship.

460 B.C.: The Russians ask the Celts for charity, begging for valuable silk while giving in nothing in return on the basis of friendship. The Celts ask the Russians where their troops were during the wars with the French, and send them home with a consolation chamber pot, decorated with a design of a loom spinning silk.

440 B.C.: The French and the Celts make a declaration of friendship, furthering the rift between the Celts and their ancient, Russian "allies."