A Peacemaker will never give up even when trying to destroy a Time Machine
After the Great World War III, the Allies reviewed the performance of the GI. They performed well, however their pistols were too weak to deal any real damage. So, the Allies trained Peacemakers after the Psychic Dominator Disaster. They possessed shotguns that could kill infantry in 3 or 4 shots.
After the time travel at the end of the Post-War Crisis, they were replaced by the Peacekeepers, who possessed Riot Shields that could deflect the bullets of an AK-47.
Peacemaker possessed Shotguns that were effective against infantry. Like other infantry, they could be run over by Tanks or eaten by dogs or bears.
Behind the Scenes
The Peacemaker looks a lot like the future Peacekeeper.