German forces also operated in the Battle of Jarama, which began with a Nationalist offensive on 6 February 1937. It included German-supplied ground forces, including two batteries of machine guns, a tank division, and the Condor Legion's anti-aircraft guns. Bombing by both Republican and Nationalist aircraft helped ensure a stalemate. It showed up the inadequacy of the Legion's aircraft, faced with superior Soviet-made fighters. The Legion's efforts only partly mitigated what was a significant defeat for the Nationalists at the Battle of Guadalajara during March.