The President of the USA is the Commander in Chief of the countries military forces. The president is the only one who can commit into a conflict or war. The U.S. military is an all volunteer force who have signed a contract that allows the President to send them wherever the President wherever their skill is needed. Every member of the military is trained to use a weapon though not all members are sent to a battle front.
For example I was in the Air Force and fixed the big bombers, the B52's and the KC135 air refueling tankers. They were not stationed and generally are not stationed directly in the battle area so I remained behind the lines, or in my case out of the country where the fighting was. My neighbor, back home, was a cryptologist in the Army and while he was in the war zone he was stationed in Saigon which during the Vietnam war was considered a relatively safe area. Another neighbor of ours was a heavy weapons specialist, a foot soldier and he was in the battle area at a frontline position.
Will he go to war depends on many differing factors starting with Commander and Chief of the Armed Forces and what the needs are for the Armed Force to be sent. Then what your friends specialty training is in and if it is needed in that deployment.
Should you worry; that too is a yes and no answer. Anyone who volunteers for the military can be sent into harm's way. Just remember our military is the best trained and best equipped military on the planet. Those who are serving in the military are just a likely to be harmed outside a war zone as in, in the same way as any of us who are not in the military.
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