the RAF and British industry failed to have the desired effect. More might have been achieved had OKL exploited the vulnerability of British sea communications. The Allies did so later when Bomber Command attacked rail communications and the United States Army Air Forces targeted oil, but that would have required an economic-industrial analysis of which the Luftwaffe was incapable. OKL instead sought clusters of targets that suited the latest policy (which changed frequently), and disputes within the leadership were about tactics rather than strategy. Though militarily ineffective, the Blitz cost around 41,000 lives, may have injured another 139,000 people and did enormous damage to British infrastructure and housing stock. RAF evaluation The British began to assess the impact of the Blitz in August 1941 and the RAF Air Staff used the German experience to improve Bomber Command's offensives. They concluded bombers should strike a single target each night and use more incendiaries because they had a greater impact on production than high explosives. They also noted regional production was severely disrupted when city centres were devastated through the loss of administrative offices, utilities and transport. They believed the Luftwaffe had failed in precision attack and concluded the German example of area attack using incendiaries was the way forward for operations over Germany. Some writers claim the Air Staff ignored a critical lesson, that British morale did not break and that attacking German morale was not sufficient to induce a collapse. Aviation strategists dispute that morale was ever a major consideration for Bomber Command. Throughout 1933–39 none of the 16 Western Air Plans drafted mentioned morale as a target. The first three directives in 1940 did not mention civilian populations or morale in any way. Morale was not mentioned until the ninth wartime directive on 21 September 1940. The 10th directive in October 1940 mentioned morale by name but industrial cities were only to be targeted if weather prevented raids on oil targets. The AOC Bomber Command, Arthur Harris, who did see German morale as an objective, did not believe that the morale-collapse could occur without the destruction of the German economy. The primary goal of Bomber Command was to destroy the German industrial base (economic warfare) and in doing so reduce morale. In late 1943, just before the Battle of Berlin, Harris declared the power of Bomber Command would enable it to achieve "a state of devastation in which surrender