It's funny, but one of the first, disturbing things that struck me about the film was the error in having postwar British Army troops in Battle Dress, cheap for costuming, but discarded long before the end of the war itself, and completely vanished in peacetime. Perhaps that's emblematic at how the movie gropes earnestly for the military soul, but misses its mark in the final, most important clinch.
Soldiers are NOT as fragile as both Mills and Guinness's character are shown to be, hence my note about 'recriminations.' I could believe that Mills's colonel had been damaged by torture and strain during the war, and that, in the end, broke him. He made some positively dreadful mistakes in the command of his regiment, mistakes that made this lifetime student of the art and science of command positively CRINGE. The man had no business being in command of a battalion, only family sentiment could have allowed him to be given a post in which he failed himself and his command so miserably.
He is shown to have collapsed, failed, and ultimately 'laid violent hands upon himself' because of the ruthless character of Guinness's character, his antagonist. All right, the cruder, rougher, 'midlands' Scot is ruthless, crude, and elemental. The obvious solution to the problem he posed was transfer, or, wiser, for Mills's character to command the battalion THROUGH him, harnessing the wind to draw the ship. All right, the damaged Mill fails to control the elements.
It does not, however, make sense that the wind itself would disintegrate after Mills's character takes what any active soldier--a man who'd seen combat, and triumphed--would have considered the coward's way out. If 'Jock' was so callous as to drive Burroughs to suicide, Jock would not have disintegrated in the aftermath, as Guinness is shown in an overlong scene doing. It did not convince. I would have ended the film when Guinness's character makes calm arrangements for the disposal of Mills's body.
I think the date of the film is the answer. In 1960, despite the best efforts of what remained of the British Armed forces, the Empire was in the later stages of headlong disintegration. Obviously, someone had to blame, and since the thin red line had broken, it had to be the fault of frail, neurotic men--such as Guiness and Mills portray.
I would say the reason for the loss of the Empire can be found in other regions. The movie IS an excellent study in command, I would recommend that officers in training view both 'Tunes of Glory' and 'The Caine Mutiny.' But both are fiction.
One note--the side-story romance of 'Jock's' daughter with an enlisted piper must needs be remembered to explain why Jock committed a very-nearly unforgivable breach of military etiquette. A Sandhurst graduate would never have thought of striking an enlisted man. A 'mustang' such as Jock had BEEN an enlisted man, and the barriers would not have been in place as strongly. Jock paid his daughter's suitor the complement of decking him.
Still, it bears repetition: Men who have bathed in blood do not disintegrate at the sight of a corpse in a washroom.