 After four months, "BdU" again called off the offensive; eight ships of 56,000 tons and six warships had been sunk for the loss of 39 U-boats, a catastrophic loss ratio.The "Luftwaffe" also introduced the long-range He 177 bomber and Henschel Hs 293 guided glider bomb, which claimed a number of victims, but Allied air superiority prevented them from being a major threat.To counter Allied air power, "UbW" increased the anti-aircraft armament of U-boats, and introduced specially-equipped ""flak" boats", which were to stay surfaced and engage in combat with attacking planes, rather than diving and evading.