In the opening scene of the bombardment of the 1950 amphibious landing at Inchon, an air strike is depicted where clearly the silhouette of an F4 Phantom is shown, an aircraft that didn't enter service until 1960.
When Truman was shown arriving at Wake Island in the Pacific, peaks and elevations of several hundreds of feet were seen. The highest elevation on Wake, which is merely a coral atoll, is only about 21 feet above sea level.
When Gen. MacArthur first meets Gen. Kenney at the airfield, the aircraft in the background are F4U Corsairs, which did not enter service until February 1943 (Gen. Kenney assumed command of Fifth Air Force in July 1942.) The national insignia on the Corsairs also dates from mid-1943.
When MacArthur is awarded the Medal of Honor, he incorrectly refers to it as the "Congressional" Medal of Honor. Although that error is common among civilians, as a General and as the son of a Medal of Honor recipient, he should have known better.
In the strategy meeting between Pres. Roosevelt, Gen. MacArthur, and Adm. Nimitz, the General addresses the President by his first name. Even if they were old friends, as the film implies, he would never have called FDR anything other than Mr. President, especially in a formal meeting.
When MacArthur is leaving the Philippines he is below deck on a PT Boat. His trench coat is totally buttoned up to his neck. The boat slows down and he immediately goes on deck. As he is shown coming on deck, his trench coat is now now open at the neck with the lapels folded back.
The general proposes landing at Leyte Beach "on the island of Luzon" in the movie. Leyte Beach, where the general made his famous landing in 1944, is not on Luzon but on the southern island of Leyte, some 500 miles southeast of the point the general indicates on the map. In fact, he is pointing to Lingayen Gulf, which is on Luzon, but is not where his first attack will be. It is where the Japanese staged their amphibious landing in December, 1941 (that eventually pushed down the island to Bataan, Manila, and Corregidor Island), and is where the U.S. forces came ashore in early January, 1945, after the first landings on Leyte in October, 1944.
Shortly after MacArthur's escape from the Philippines in the spring of 1942, he complains that the President and the Chiefs of Staff are not sending him enough troops, supplies, and equipment to carry on his war against the Japanese. He says that priorities are instead being given to commanders in other theaters, including Gen Patton in North Africa. However, Patton's troops did not arrive in Africa until November 1942.
In the invasion scene of the return to the Phillipines, the soldiers storming the beach are dressed as U.S. Marines were in WWII in the South Pacific. The invasion was an all Army show and soldiers did not routinely wear camouflage helmet covers nor leggings. This was probably done to match up actual combat footage since the Navy and Marine Corps filmed a great deal of combat footage in color.
The film clip of the atomic bomb exploding in the film is obviously meant to represent either the bombing of Hiroshima or Nagasaki (or perhaps even the first bomb test at Los Alamos). Yet the film clip used shows a United States bomb test over the ocean and these US ocean tests did not take place until well after WWII had ended.
In the very opening scene on the parade ground at West Point, General MacArthur's flag is shown as having a red field with a square of four stars with the fifth star in the center. The proper flag for a 5-star General of the Army (as seen in photographs of the real-life event) has a red field with the five stars in a ring, with the center space in the shape of a pentagon, the same pattern as the actual rank insignia.
During the 1945 combat scenes in the Philippine Islands, several American M1 Carbines can be seen with bayonet lugs mounted under their barrels. In actuality, these lugs were not added until the Carbines were overhauled by government armories after World War II ended.
In the command bunker on Corregidor, MacArthur's aide, Sid Huff, knocks on the the door to MacArthur's office and Ah Cheu, Arthur MacArthur's Nanny (that was really her name - she was listed on the passenger manifest for PT 41, the boat on which the MacArthurs fled Corregidor), answers the door and incorrectly refers to Huff as "Major." At the time Huff was a Lt. Colonel and is wearing the silver oak leaves denoting that rank. While it's possible the error was intentional to show an unfamiliarity with military rank, it is not likely the General's house staff would not know the proper ranks.
General MacArthur, President Roosevelt, and Admiral Nimitz are seen conferring on board what looks to be some kind of transport type vessel. They actually conferred aboard USS Baltimore, a heavy cruiser. Note the lack of big guns when the three meet with reporters.
In the beginning of the film (and also in a briefer moment later), there are Japanese planes bombing soldiers on the field. However, you can see no bombs carried under the planes, nor being dropped from them - just a swoop of the plane and an explosion on the ground to coincide.
When MacArthur has his car stop to let the Soviet military officer out, the rear projection footage behind suddenly stops moving, so that leaves on a bush which had been visibly blowing in the breeze abruptly freeze in place.