For me it has to be, Adolf Hitler: My Part In His Downfall, by Spike Milligan.
His tour of old battlegrounds led of course to his part in Life of Brian. Did some acting on set, then trekked off to see the old battlefields where he and his Eighth Army mates used to be.
And if you're interested in comedians writing WWII memoirs, may I point out Quartered Safe Out Here by George MacDonald Fraser, about a less frequently covered theatre of war (Burma with Slim's Forgotten Army). Although Fraser makes it plain that he saw nothing of a theatre, merely marching back and forth for no discernable reason before hearing of Slim's strategic brilliance that involved Fraser marching back and forth.
"I went off to renew acquaintance with projector, infantry, anti-tank, commonly called the Piat. It was the British counterpart of the American bazooka, and might have been designed by Heat Robinson after a drunken dinner of lobster au gratin. It's easy to describe, and I may have forgotten some of its finer points, such as its exact measurements, but I'll do my best.
From memory, then, it consisted of about four feet of six-inch steel pipe, one end of which was partly cut out to leave a semi-cylindrical cradle about a foot long, in which you laid the bomb. At the other end of the pipe was a thick butt pad which fitted into your shoulder when you lay on the ground in a firing position, the body of the pipe being supported on a single expanding leg. The bomb, a sinister black object fifteen or so inches overall, had a circular tail fin containing a propellant cartridge, a bulging black body packed with high explosive, and a long spiked nose with a tiny cap which, when removed, revealed a gleaming detonator.
Within the body of the pipe was gigantic spring which had to be cocked after each shot:you lay on your back and dragged the Piat on top of you, braced your feet against the projecting edges of the butt pad, and heaved like hell at something or other which I've forgotten. After immense creaking the spring clicked into place, and you crawled out from under, gamely ignoring your hernia, laid an uncapped bomb gently in the front cradle, resumed lying firing position, aligned the barleycorn sight with gleaming nose of the bomb, pressed a massive metal trigger beneath the pipe, thus releasing the coiled spring which drove a long steel plunger up the tail fin of the bomb, detonating the propellant cartridge, you and the Piat went ploughing backwards with recoil, and the bomb went soaring away - about a hundred yards, I think, but it may have been farther. The whole contraption weighed about a ton, and a bombs came in cases of three; if you were Goliath you might have carried the Piat and two cases."
- George MacDonald Fraser