 Complete the following phrase:  On his release in August 1935, he travelled to Spain where in July 1936 he joined the International Brigades in support of the Spanish Republican cause, becoming Chief of Staff for Lieutet Colonel Hans Kahle in the XI International Brigade and the 35th Division. He was in Madrid in November 1936 writing training booklets for the military command as the city became increasingly under threat. He was driven out of the city to Cuenca by Claud Cockburn, a British communist journalist, under orders from the government and their Russian advisors. In November 1936 he became leader of the Thälmann Battalion of the XII International Brigade, fighting in the Battle of Guadalajara in March 1937 and then in the 