There were two primary uses for nuclear weapons in the Vorkosigan Saga: one was for taking cities hostage, as happened with Vorkosigan Vashnoi during the First Cetagandan War, and the other was for capturing wormholes -- an attacking force would send a sacrifice ship through the wormhole and have it set off a "sun wall," a large number of nuclear explosions in a small area; this destroyed everything in the immediate vicinity. Nuclear antipersonnel mines probably could not fit in a person's back pocket.