NAM-1975 is an arcade game, released in 1990 by SNK.
The game is set in a very fictional account of the final months of the Vietnam War. The story begins with the two soldiers entering to war to rescue Dr. R. Muckly, an ex-scientist of the American Army, who has been kidnapped by Northside Terrorists. Nancy Muckly, Dr. Muckly's daughter has also been kidnapped and is presumed imprisoned in the NAM interior.
However, as the game progresses, the armies learn that Dr. R. Muckly is a madman who is building a gigantic laser cannon to take over the world himself (the final boss battle was infamous for disallowing continues, except by modifying the DIP switch).