Murray Leinster 
Morale [PDF ebook] 
A Story of the War of 1941-43

Written before the outbreak of World War II, this remarkable story imagines a military conflict in which a weapon of unprecedented power and destructiveness is unleashed — but this time, it’s an enemy of the U.S. that has the upper hand. With entire cities swept off the map in a matter of seconds, will the country be able to fight back?