sentences:  Reserve of the Main Command included howitzer regiments (48 pieces) and heavy howitzer brigades (32 pieces), sometimes organized into artillery divisions.By the outbreak of German-Soviet War older 152 mm howitzers were being replaced by the newer M-10.However the M-10 production rate was slow, so by June 1941 the M1910/37 was still in service and was employed by the RKKA in the German-Soviet War.