How would ancient Vikings react to a gun-wielding giant with flaming red hair? What would a modern cop do in a feudal world where gunpowder was considered a benediction of God? What if Scipio Africanus never lived to challenge, or kill, Hannibal at Zama? The probabilities are end-an infinite number of ways to replay the same scene, over and over again. War transmuted to its highest magnitude, ripping through the very fabric of time. Features stories by Poul Anderson, Anne McCaffrey, Harry Harrison, Keith Laumer, John D MacDonald, Bob Shaw, H Beam Piper, and Randall Garrett.