Thank You For Your Service

Riddle: Every day, some of America's finest fall into enemy traps and are captured and placed behind bars. The olive-green and greenish-brown camouflage uniforms they wear don't appear to be effective in protecting them against these enemies. Once caught, there is rarely any chance of escape for any of these prisoners. In fact, nearly all of them are executed by their captors, but never once has even one of them ever revealed any state secrets before dying. Each prisoner is systematically removed from his/her cell by an executioner wearing a white uniform and hat. This killer appears to have no conscience, as he ends the lives of many of these captives each day by scalding them to death. However, there are many Americans who want to honor these and celebrate the lives of the fallen. In fact, 44 U.S. states have erected monuments to remind us of those who have given their lives to serve us. Who are these captives, and what are these monuments which have been erected to help us remember them?