Movie: ****The Bridge Over the River Kwai (1957)

This is one o those stories where sometimes the means don't justify the end.  In order to build morale of their men, the officers at a prisoner of war camp run by the Japanese with Allied prisoners, determine that they should participate in the forced labor required by the Japanese, but not only participate but do a good job.
At the same time, the Allies send a team to blow up the bridge being built by the prisoners.  In the end, these decisions pit Colonel Nicholson (Alec Guinness) against Shears (William Holden) one of the Allies who has come to blow up the bridge.  When Nicholson discovers the plot, he informs the Japanese, but then realizes his mistake.  "What have I done?  What have I done? he exclaims, as he depresses the plunger to blow up the bridge.  Classic scene.