The Carbines used by the Marines all appear to be the World War II M1 model. By the time of the Korean War, the improved M2 Carbine featuring a bayonet attachment, fully adjustable rear sight, and longer 30-round magazine was standard issue.
In several dubbed-in film clips of actual aerial combat, Douglas SBD Dauntless dive bombers are seen attacking the enemy. The Dauntless was obsolete by the time of the Korean War, and none were used in combat during that conflict. These film clips would have been taken during World War II.
At battalion headquarters at Camp Pendleton, the executive officer announces the arrival of Captain Hansen to Lt Colonel Corbett, the battalion commander. But the exec addresses Corbett as 'general' instead of 'colonel.'
Right after the Marines stop the huge communist attack near the end of the movie, Captain Hansen gets out of his foxhole to check on his men. Nearby are dozens of fallen enemy troops. If any of these soldiers were just wounded or pretending to be dead, they could easily have shot Hansen, since he was fully exposed to them. A real Marine officer would never have been this careless.
When Capatin Hansen's company enters a town soon after coming ashore, they are fired on by a machine gun crew hidden in a building. The Marines immediately take cover, but Hansen gives no orders to his men for almost five minutes. In an actual situation, the officer in charge would immediately have begun issuing orders for his troops to eliminate the enemy position.
When first reporting to his new battalion commander in his office at Camp Pendleton, California, Captain Hansen does not salute him. Marines always salute their superior officers in such instances, except when in combat areas.
>> This is wrong. Marines never salute bare-headed.