It seems like Major Force did die. I think it was in the first Superman/Batman arc. But Major Force is like Captain Atom and its pretty much impossible to kill him off since he's made of energy. I guess he just reformed. I can buy that one moreso than most characters coming back from the dead without explanation. And who knows...this could be a different guy in the uniform.
Major Force has developed a knack for surviving death due more to editorial negligence than any explained power. He died and was buried in the ground once upon a time where he remained until he was brought back by Resurrection Man. After that every time he died the next writer would just bring him back with no explanation other than he's defied death so many times that he's now just unkillable. To the extent that Kyle Rayner once decapitated him and the head kept on talking. He's not made of energy like Captain Atom, at least he didn't used to be, he had the power to absorb and emit a black oil-like mass the way Atom could produce or absorb energy. At some point the writers forgot and just started treating him like he had the same powers as Atom without explaining why. But even Captain Atom doesn't die and resurrect like that. His "deaths" have usually been caused by an explosion and he doesn't die, he simply absorbs the energy which causes him to shunt into quantum space and he reappears in another place/time. People assume he's dead but he's not. As opposed to Major Force whose deaths have usually been caused by bodily dismemberment which he just heals from for no particular reason.