When must the watch-to-watch inventory take place?

The watch-to-watch inventory must take place when watch personnel change to ensure that all sensitive materials, such as classified documents and communication security (COMSEC) materials, are properly accounted for at the transition of shifts. This practice is crucial for maintaining the integrity and security of the materials from one watch to the next, preventing any potential loss, unauthorized access, or mishandling. By conducting this inventory during personnel changes, the incoming watch can verify that they have received all necessary materials in good condition and confirm that all outgoing personnel have returned any items they were responsible for. This process also reinforces accountability among the personnel and helps mitigate risk during the transition.

The other options may suggest periodic checks or reviews, but they do not align with the immediate need for accountability that is paramount whenever personnel changes occur.