I’m a veteran of the US Army, 4 years active duty and 4 years IRR. I had service during Desert Shield/Desert Storm and the Cold War in Signals Intelligence. If you want to support those in our military, be political and not in a knee jerk way but in an informed way. The best thing you can do for those serving is to insure that their lives are not put on the line for economic reasons, or for ego or to support democracy by supporting dictators (how does that compute?). Tattoos are only symbols just like words. If not backed by action they mean nothing.
If you insist on a tattoo, I agree with the suggestion of a peace symbol. If you want to support militarism and patriotism as the knee jerk reaction of the right wing whose idea of service to our country is a three martini lunch with a lobbyist from a defense contractor, then get a peace symbol in a set of cross-hairs.