Peckham, Howard H. Why The British Lost The American Revolution. Fort Wayne, IN: Allen County-Fort Wayne Historical Society, 1963. First Edition. 
5 1/2 x 8 1/2 inches, portrait of author, 14 unnumbered pp. Very good. Pamphlet.
Peckham reviews reasons that many writers had given, but concludes that there were two main factors.
The first was that the British were fighting a people, not merely an army, a concept that exasperated the home office. The British leaders could not understand why American civilians would take up arms over and over, and not leave things to the official armies.
Second, the person of George Washington. As a leader he fought a war of attrition, and led his army gallantly. He was never understood by his enemies, "that a man could be defeated again and again without being conquered frankly puzzled them."