Nicholson's mentioning India and his use of the Indian word "coolie" indicates he was a member of the British Raj. The Englishmen of that generation were men of great honor and loyalty, but also men who believed in their own supremacy and wanted things done his own way - traits Nicholson displays.
After the bridge is destroyed, Warden and the female bearers start back for home. Major Clipton is left to mutter, "Madness!" in horror of what has just happened. Clipton and the wounded and sick British prisoners are stranded in the middle of the jungle, with no feasible way to get to civilization. The body count will likely go up quite a bit in the next few days.
The bridge has been destroyed and Nicholson killed, but there's still an entire battalion of British soldiers out there who Nicholson unwittingly conditioned into cheerfully doing quality engineering work for the Japanese, happily marching to a new work camp. How much more will they build for the Japanese before they either come to their senses or get wiped out by some follow-on mission by their own countrymen?
