Well, everybody knows Napoleon invaded Russia due to AGW. Fairly certain Attila swept across Asia for the same reason. The Khan’s? Pretty sure it was due to the lack of hot women and spaghetti sauce.
While the Napoleonic Wars do not appear to be climate related, the migration of the Huns under Attila probably was. The migration westward of the nomadic central Asian tribes created pressure on the Germanic tribes to overrun the Western Empire in the late 4th and 5th Centuries. This coincided with the end of the Roman Warm Period, a prolonged period of time of warmer climate than what we are experiencing today. During the warm period, Rome prospered. At the end of the warm period, Rome declined and fell. The western world was subjected to a colder climate, and with it, "the Dark Ages."
So Gore and his minions turn history on its head. Warm = Prosperity = Civilization = Good. Cold = Harship = Dark Age = Bad. Now why is it again we want it to be cold?