The American withdrawal was hastened by an increasing shortage of ammunition. Fortunately for the defense, three tank destroyers of 644th Tank Destroyer Battalion arrived with a good supply of bazookas and anti-tank mines. These reinforcements were put to good use when the 12th SS Panzer Division launched a powerful tank and infantry attack on Rocherath-Krinkelt. The American forces responded with a powerful artillery barrage supported by mortar fire, bazooka rockets, and anti-tank mines that repelled the German attack around midnight of 18 December. The German attack failed to clear a line of advance for the 12th SS.