Unless you've had that kind of experience, "combat" and "war" are abstractions.
Agreed. And it's more the "experience" than the knowledge. Anyone can read and become an expert at war given an adequate IQ and desire, but to actually understand where you're sending your troops.. you need the experience of having done so.
I don't think many will argue that national defence/sovereignty of the Nation is a Presidents most important role. The experience of serving, of being either the one who sends or gets sent.. in an invaluable aid no adviser can adequately explain.
I also spent 4 years on the SDPD riding patrol and other various duties. I quit and went back to the military despite 3x the pay and benefits and frankly I loved the job. So why go back? Because the city of San Diego decided to have a civilian shooting review board without any prior law enforcement experience. I knew in my mind and in my heart they could never know what it was like to be me, walk down that dark alley, face down lopsided numbers, or even walk up to a car you stopped at night. So how could they adequately represent my decision to shoot? (much less decide my fate, freedom, and future) There is no way they could. Without having a gun pointed in your face not knowing if the guy was going to pull the trigger or not.. you just can't know what it feels like. Or what it does to you even years later. I left and went back in the service.
During all the years I served I noted a huge almost seismic shift in attitude towards the CIC, respect, confidence in actions, and belief in our tasking.. between different Presidents. Carter was laughed at, Reagan was almost a deity, Bush Sr. was respected, Clinton was hated like no other, and Bush Jr. respected.. though that lessened..
I'll go further. I think every man and woman should serve their country for at least a two year stint. Military, duty in nursing homes, forest firemen/smoke jumpers, duty in a public morgue, and should as a rule do this service away from their home town and support system. Show me you have what it takes to give back to your country in a way we can believe is a "sacrifice" and I'll give you a chance to lead me.. or follow me.