In 1939, Germany seized all 17 pieces from Czechoslovakia and repaired the howitzer from the Arsenal Museum, designating them "30.5 cm Mörser (t)". In 1941, they obtained five more weapons after the defeat of Yugoslavia and placed them into service as the "30.5 cm Mörser 638(j)". They saw service against Poland, France and the Soviet Union in World War II, where they served with Heavy Artillery Battalions ("schwere Artillerie-Abteilungen") 624, 641 and 815 as well as two Heavy Static Artillery Batteries ("schwere Artillerie-Batterie bodenstandig") 230 and 779.