Abstract: A fuze mechanism for projectiles and the like is provided with a number of integrated safety catches which must be successively released before the fuze may be detonated. A firing pin lock cannot be released until the fuzing time has first been set. Release of the lock and the firing pin is also prevented by a centering piston response to inertial forces at the time the projectile is launched and another piston controlled by the clockwork of the fuze. The clockwork may be overridden by mechanism detecting impact of the projectile to permit detonation in a period of time shorter than the fuzing time.