The first of two volumes recounting in sweeping (almost too sweeping) detail the true impact of Nazi Germany's storied U-boats on the course of WW II. On the basis of his painstaking research, Blair (Ridgway's Paratroopers, 1985, etc.) concludes that this impact has been greatly exaggerated. Noting that 99 percent of the Allied merchant ships in transatlantic convoys reached their destination, he suggests that the principal achievement of the U-boats may have been obliging Anglo-American forces to commit substantive resources to anti-submarine warfare. Without ever suggesting that the Battle of the Atlantic was other than a bitter, to-the-death struggle on both sides, the author (who saw action aboard a US sub in the Pacific theater) makes a persuasive case for his revisionist thesis. In doing so, moreover, he offers gripping, hell-and-high-water accounts of submarine warfare. Blair provides background on the post-WW I revival of the German Kriegsmarine, and on the command structure and aspirations of the Third Reich's silent service. The author then reckons the havoc wreaked by their skippers before and after the US was drawn into the global conflict. Covered as well are the exploits of legendary aces, the logistical problems attendant to deploying a flotilla of U-boats, rules of engagement, the invariably inflated tonnage claims, and code-breaking programs. For all the terror U-boats inspired among mariners and upper-echelon commanders, Blair argues that they never proved a decisive strategic weapon; in fact, these craft were doomed early on by a ruinously unfavorable exchange rate (the number of ships sunk per subs lost) without ever posing a serious threat to Allied supply lines. Military history of a surpassingly high order, which (assuming no letdown in the concluding volume) could become the standard reference on U-boats.