OPSEC is the process of identifying mission vulnerabilities and deploying methods to minimize exploitation by hostile or otherwise adversarial forces. OPSEC begins at home in the barrack and should be incorporated into every activity you undertake.
OPSEC is an ongoing, ever-present concern that should be revisited in training environments regularly. The more critical your mission, the harder the competition will try to get the essential information you have. Designated specialists should be constantly assessing vulnerabilities and educating operators and rear echelon support in how to most effectively protect sensitive information as the opposition develops tactics to obtain it.
OPSEC should ultimately permeate every aspect of military personnel's lives. Even the lowest ranking service member possesses information that can be exploited to impede the mission. Therefore, all service members should be trained to be very aware of surroundings and always behave as if being observed.