Gordon Williamson 
U-Boat Crews 1914 45 [PDF ebook] 

If one single weapon in Germany’s arsenal can be said to have come closest to winning the war for the Third Reich, it was without doubt the U-Boat. German U-Boat technology, training, tactics and combat successes far exceeded those of any of the other combatant nations, and even as the Third Reich was crumbling, technically advanced vessels such as the Type XXI, many years ahead of its time, were being put into volume production. Gordon Williamson provides a fascinating overview of the achievements of the U-Boat Waffe in both wars, together with a study of the uniforms and insignia worn by U-Boat crews.