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.
Factual error: The shot of the atomic bomb exploding, presumably Hiroshima, is of a later test, as you can see ships anchored in the test area. The footage is from post World War 2 testing.