Enter A Soldier. Later: Enter Another — Robert Silverberg

In the mid 21st Century the United States is a sleeping giant, lost in dreams of faded glory. But in one field we still reign supreme: entertainment, which in this future means computer simulations. That's why it is in America that the final computer breakthrough is achieved, the simulation of genuine thinking, feeling personalities from history: Elizabeth I, Ghengis Khan, Pizarro, Socrates, Moses and Joan of Arc. You can see them all in action, with and against each other, in a world they never made -- but just might remake closer to their silicon hearts' desire.