A safety and arming unit for a fuze of a projectile has a rotor for interruption of a firing chain. The rotor can rotate from a safe position to an armed position. In order to allow the safety and arming unit to be designed to be physically compact and such that it can be assembled easily, it is proposed that it has a first and a second rotor safety device which each engage in the rotor in order to block rotor rotation to the armed position, wherein the first rotor safety device is designed to carry out a release movement by virtue of its inertia during a launch acceleration of the projectile, and the second rotor safety device has a pyrotechnic charge for producing a release movement.