Babylon 5

A technomage named Galen predicts an imminent attack by the Drakh, the old allies of the Shadows. Through dreams, a thief, a captain, and a president are brought together to head them off. The president is John Sheridan. Because of his irrational behavior, Sheridan's friends begin to wonder about his sanity. It's up to all of them and two prototype battlecruisers, the Excalibur and the Victory, to stop the fleet and their planet-killer. But is there more to the Drakh's plan?