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, including Ju 52s from the Legion, helped ensure a stalemate. It showed up the inadequacy of the Legion's aircraft, faced with superior Soviet-made fighters. Von Thoma requested Irish nationalist support for a tank advance at one point, never to be replicated. Use of He 51 and Ju 52s, and the Legion's anti-aircraft guns used in ground roles, only partly mitigated what was a significant defeat for the Nationalists at the Battle of Guadalajara during March. A joint Italian-German general staff had been set up in January 1937 to advise Franco on war planning. The defeat of a significant Italian force and the growing Soviet superiority in tanks and aircraft led the Germans to support a plan to abandon the offensive on Madrid and instead concentrate a series of attacks on weaker Republican-controlled areas. Whilst many countries believed motorised troops had proved less effective than was first thought, the inadequacy of the Italians as a fighting force was quite apparent to the Germans.