Permanent alliances are fun--especially when your enemies become PAs. One recent game (Medium and Small) I was playing? I had Tokugawa and Boudica PA up and form a superpower on the far side of the world. I had control of 3 religions and decided to invade Tokugawa, so I kept research up by 90% and built a large invasion fleet. In short, I had to wait for Plastics to get the ONLY source of oil, which was offshore from a research factory. Basically I had to build a super invasion fleet complete with Infantry, Fighters, Bombers, Calvary, and Cannons. Early in the game, I eradicated Mansa Musa from MY continent and MY large offshore island. Built transports, destroyers, and all that fun stuff and setup the transport. Stopped the fleet in Mansa Musa's two cities nearest to Tokugawa's island cities, captured about 3-4 of them, and then went for a mainland invasion. Two or three coastal cities down (and equipped with fighter & bombers to soften up other city defense), I call a ceasefire. Setup troops for next invasion and declare war. Invade about 3 more cities on the wide part of his long continent and send a small invasion fleet off to some out-of-the-way islands, so I wouldn't have to play much cleanup of his insignificant islands. In short, I destroyed his civilization and had Boudica (the strongest, behind me) furious at me, ready to declare war at a moment's notice. In short, I went for an easy space victory... I just really wanted to destroy Tokugawa... such a pain to demand tribute from!