From the book’s conclusion,
In 1939-1942 German infantrymen were the best trained and most efficient soldiers in the Western world. Their victories in Europe optimized the use of new technology and old skillsets to overpower their enemies in a series of lightning thrusts. Spearheaded by airborne special forces and amor, fully supported by a rampant air arm, quite simply they blew away the opposition and made fools of the Allies who had defeated an older generation of Germans so comprehensively in 1918.