Allied armies began using combined arms formations and deep penetration strategies that Germany had used in the opening years of the war. Many Allied operations in the Western Desert and on the Eastern Front, relied on firepower to establish breakthroughs by fast-moving armoured units. These artillery-based tactics were also decisive in Western Front operations after Operation Overlord and the British Commonwealth and American armies developed flexible and powerful systems for using artillery support. What the Soviets lacked in flexibility, they made up for in number of rocket launchers, guns and mortars. The Germans never achieved the kind of fire concentrations their enemies were capable of by 1944.