Factual error: Just after the start of the Korean War, McArthur places a map of Korea on the hood of a jeep to explain to a subordinate general his plans to invade Inchon. The map shows the boundary of North and South Korea not along the 38th parallel, which was the border at the time (1950), but along today's DMZ - not established until the Korean armistice was signed in 1953.
Factual error: During MacArthur's briefing to FDR, he intends to land troops on Leyte Beach, but points to a spot on Lingayen Gulf on the island of Luzon (another beach landing site). Leyte Beach is in the Visayan Islands. A bronze monument stands there today to commemorate that landing. This is also where he made his "I Have Returned" speech.
Other mistake: In the earlier part of the movie (at Corregidor Philippines) where Japanese warplanes are bombing the field camp, it can be seen that a warplane approaching its target can be seen with no bomb attached underneath, and yet an explosion takes place on a targeted machine gun position. The action scene is repeated minutes later, this time hitting the escaping and running soldiers.