P. G. Wodehouse 
Swoop! [PDF ebook] 
Or How Clarence Saved England: A Tale of the Great Invasion

Only a comic genius of the magnitude of P.G. Wodehouse could take a weighty subject like war and turn it into a rib-tickling joyride. The Swoop! is an account of a fictionalized invasion of England by several enemy armies — and of the indomitable Boy Scout leader who uses psychological warfare to turn the leaders of the invading forces against one another.