Corrected entry: The rifles used by the Japanese guards appear to be Lee Enfield Mark 3 models of World War 1 vintage and used by the British Army.
Corrected entry: The commandos going to blow up the bridge are covered in black tar (or paint) when they are finished setting the charges. But in the morning they are almost clean.
Correction: You don't think they would make cleaning their night camouflage off their faces an urgent priority, to stop the Japanese guards identifying them? They have hours to wash their faces.
Corrected entry: In the final scene, when there was a skirmish between Alec Guinness, bridge demolition team and the Japanese soldiers, Guinness eventually falls on the detonator which blows up the bridge. But after that, all the Japanese soldiers just disappeared. Did that one guy with a mortar and a bunch of women take them all out?
Correction: There were not that many Japanese soldiers that left the bridge and we do see several bodies which is plausible given that the Japanese were in the open while the Brits were under cover. The other Japanese were killed in the bridge explosion.
Corrected entry: When the British POW's are marching into the Japanese camp whistling Colonel Bogey, as they march behind Alec Guinness, you can see one of the British soldiers swinging the same leg and arm at the same time.
Correction: While unusual, this is by no means unheard of. It's the curse of drill instructors everywhere.
Corrected entry: The bridge constructed by the British was in reality metal - and it's still there.
Correction: The story of the "The Bridge on the River Kwai" is not the story of building a single bridge. It is the story of WWII allied POWs forced under horrific conditions to build the Thai-Burma railroad for the Japanese Army. The railroad constructed was 415 Kilometers long and included 688 bridges, 680 of which where made of wood. For most of the railroads length it somewhat followed the route of the River Kwai and actually crossed it several times. When the railroad was completed, many of the bridges along its length where bombed and destroyed by allied air raids and had to be rebuilt. As such the wooden bridge in the movie is a composite representation of all the bridges.
Corrected entry: Alec Guinness gets a bloody nose after Colonel Saitu slaps him across the face with a flimsy Geneva conventions rule booklet. A paper cut would have been more realistic.
Correction: Although the book is flimsy, its spine would have been heavier due the pages being pressed together there and from the weight of the glue. Thus being hit in the nose with the spine could easily open a capillary in the nostril and cause the nosebleed.
Correction: With the fall of Singapore the Japanese captured enough weaponry to equip an army, much of it World War 1 vintage. They used this booty to equip their low priority operations, including prisoner of war camps.