You dont not sign a contract of employment to join the forces you pledge allegieance to basically go where your Commander in chief send you. In our case the Government of the day on behalf of the Queen who our C in C. As a constitutional monarch she is the figurehead for government policy. If she refused there would be a constitutional crisis. So basically you can't say I'm a clerk it isn';t in my contract I don't do infantry stuff. We say actually you signed up to be a soldier and that quite possibly means you lay your life on the line that is part of being in the forces. My son has seen this from both sides over here as a TA soldier and as a full time meber of the army either way the commitment is the same. As I say this is only the view from the UK.
Maureen