On 21 February 1916, the German 5th Army began an offensive which started the Battle of Verdun. Douaumont was the largest and highest fort on the two concentric rings of forts protecting the city and thus the keystone to the city defenses. The German offensive was already four days old and progressing rapidly from the north when, on 24 February, it came within reach of Fort Douaumont. Fort Douaumont was still only manned by a maintenance crew of only 56 troops and a few gunners. The highest-ranked soldier in the fort was an NCO named Chenot. On 25 February, elements of the German 24th Brandenburg Regiment ("6 Infanterie-Division, III Armeekorps") approached Fort Douaumont from the north, as a reconnaissance or raiding party. Most of the French garrison had already gone to the lower levels of the fort to escape the incessant German shelling with large-calibre guns. A battery of super-heavy 420 mm "M-Gerät" howitzers was intermittently pounding the fort, damaging the 75 mm gun turret.