The Knights of Arthur

First of all, Arthur was a machine. He rode out the missile attack that shattered the United States safe at sea aboard a hospital ship. But when he took to land with two friends -- human friends -- that's when things got dicey. Because an Artificial Intelligence with his skills could do a lot of work, and quite a few people wanted him. Preferably without his human friends in tow... A classic from the Golden Age of science fiction!