Country Joe McDonald, of Country Joe and the Fish, was let out from the US Navy. He sang this 1967 song a few years later, at the original Woodstock, kind of on a lark and against his wishes.
It became an anthem against the Vietnam War, which is the “next stop,” meaning more deaths to come in more places. With this “GI humor” and a dollop of nihilism, it blames political leaders for the war. It denigrates large corporations that profit it. Soldiers are expendable pawns.
The song was also controversial for being borrowed in composition from an old ragtime tune. And of course, for the F-word “F.I.S.H.” cheer that sometimes introduced it.