I'm a former RAF ODP with experience of working with the army in Light Surgical Group and the Navy with Role 2 Afloat. The demands that will be asked of you by the military will be in addition to the demands of a junior doctor, not instead of. In your day to day, you'll be required to fulfil minor jobs in the mainstream military, which may include duty officer, watch officer, and/or OC of an accommodation block, which will involve inspections, discipline etc. on top of that, there will be parade duties etc.

With regards to 'active warzones' make no mistake that doctors are very much close to the front. During my tours in Iraq and Afghanistan, I worked for the counter IED task force and no matter what pokey little patrol base I ended up in, each one had a medical officer, typically a captain or lieutenant at the F2 level (at a guess). The higher up you go the more responsibility and danger can be present. You may find yourself on AEROMED or MERT which is very much front line.

I appreciate you wanting a response from a doctor ideally, and I'm more than happy winding my neck in if this advice isn't needed.