Based on the experience gained in World War I and the technological and organizational developments of anti-aircraft forcesin the interwar period, Germany's political and military leadership entered the Second World War with high expectations for the Luftwaffe'sground-based air defenses. These expectations were tied to a standard that measured success based simply on the number of aircraft shot down.Despite the success enjoyed by the Luftwaffe's flak defenses between 1939 and 1945, many Luftwaffe leaders demonstrated a limitedunderstanding of the broader outlines and effectiveness of Germany's ground-based air defenses. These men repeatedly were guilty ofevaluating the performance of the Luftwaffe's air defenses using a simple binomial equation that compared flak with fighter performance.This myopic focus on fighters versus flak led the Luftwaffe's leadership consistently to ignore or grossly underestimate the contributions of other elements of the ground-based air defensenetwork. German flak defenses accounted for at least half of American aircraft combat losses during the war and an estimated thirty-sevenpercent of Bomber Command's missing aircraft during night raids, while anti-aircraft fire damaged more than 66,000 U.S. bombers and over 9,000British bombers. Anti-aircraft defenses not only destroyed and damaged aircraft, they also severely degraded bombing accuracy by drivingbombers to higher altitudes and inducing evasive maneuvering on the final bomb run. Flak damage also crippled Allied aircraft making themeasy prey for Luftwaffe fighters. However, Luftwaffe leaders largely ignored these "hidden" effects by focusing solely on the number ofaircraft destroyed. Likewise, they often failed to recognize the outstanding returns achieved by decoy and deception measures atrelatively low cost, despite the large number of Allied bombs that fell on these sites. Another example involved the critical support providedby searchlights to night fighter forces at different stages of the conflict, as well as the contributions made by smoke generators and barrage balloons to point defenses. In the end, the Luftwaffe'sground-based air defenses provided a capable and effective adjunct to the Third Reich's fighter defenses; a contribution largely ignored orunderestimated by both contemporary Luftwaffe leaders and post-war historians of the air war.