12 O'Clock High

Here's To Courageous Cowards (1x11)

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Corporal Lawrence, a mild-mannered desk clerk, stows away aboard a B-17 to try his hand as a gunner and actually turns out to have a good eye. Major Morse, the pilot and group commander when Savage isn't flying, is so impressed, he urges Lawrence to get accelerated training and become a full time crew member. To his dismay, Lawrence balks at the offer, and Morse subsequently learns that he was a conscientious objector before he enlisted.