Because of my faith, I struggled with the morality of it too. At the risk of starting a political debate, I decided that, in the end, the military is no more immoral than law enforcement or surgery to excise cancer. Yes, mistakes can be and are made in all of those professions as we have collateral damage, false arrests and removing extra tissue, but human society cannot thrive in anarchy; we need cops, soldiers, surgeons and people to toss out trash: unpalatable societal functions but necessary. It's been said that wars are unnecessary, and our problems could all be solved through diplomacy. This is hypothetically true, but unless we put all of mankind of Ritalin or other behavior-modification drugs, someone somewhere will always be ready to start something, and we'd be fools to be unable to defend ourselves or our friends.
Bottom line is, ethics aside, the military helped me find focus, structure and discipline, skills to function better in the NT world.