The burden of the initial defence of the city fell on the 1077th Anti-Aircraft Regiment, a unit made up mainly of young female volunteers who had no training for engaging ground targets. Despite this, and with no support available from other units, the AA gunners stayed at their posts and took on the advancing panzers. The German 16th Panzer Division reportedly had to fight the 1077th's gunners "shot for shot" until all 37 anti-aircraft guns were destroyed or overrun. The 16th Panzer was shocked to find that, due to Soviet manpower shortages, it had been fighting female soldiers. In the early stages of the battle, the NKVD organised poorly armed "Workers' militias" similar to those that had defended the city twenty-four years earlier, composed of civilians not directly involved in war production for immediate use in the battle. The civilians were often sent into battle without rifles. Staff and students from the local technical university formed a "tank destroyer" unit. They assembled tanks from leftover parts at the tractor factory. These tanks, unpainted and lacking gun-sights, were driven directly from the factory floor to the front line. They could only be aimed at point-blank range through the bore of their gun barrels.