The morning of 29 July began with preparatory artillery fire of 25,000 shells fired by the Soviets. The bombardment covered the Tannenberg Line in a dust cloud. The forest on the "Sinimäed" Hills was entirely destroyed, with the trees cut down to a height of 2–3 metres. While having a great psychological effect, the ""Katyusha"s" or so-called "Stalin organs" were inaccurate, causing little damage to the well-dug-in German troops. The 70–80 German "Nebelwerfers" answered. This was followed by Soviet bombers trying to hit the last of the German troops, ducking down in their trenches. Dressed in camouflage uniforms, they remained unseen by the Soviet pilots.