That's an ideal, not the reality. The reality is actually pretty frequently similar to the private sector - someone is the only person who knows how to do somet

That's an ideal, not the reality. The reality is actually pretty frequently similar to the private sector - someone is the only person who knows how to do something, they leave, and they're replaced by someone who doesn't know how to do it and picks things up as they go along. It's one of the reasons why militaries can feel pretty dysfunctional. The only way of ensuring that people are adequately replaceable is to have formal training programs, and the only way of ensuring that those training programs improve over time is to have a feedback loop to take in lessons from the field and to keep abreast of updates to the state-of-the-art. Ultimately this is too costly, even for militaries, with possible rare exceptions in small special-ops type units where people do rotate between operations and training and rarely de-facto leave the unit and as such, do not suffer from the same manpower pressures of most military units while enjoying attention of upper management when desired.