There were around 70 T-26s in the Republican Army in the beginning of 1937. In February 1937, company-sized detachments of the Tank Brigade participated in the Battle of Jarama. On 14 February 1937 the Tank Brigade, together with the 24th Infantry Brigade, took part in a counterattack and overcame a major Nationalist force, causing about 1000 Nationalist casualties. On 27 February 1937, the Tank Brigade launched five attacks on Nationalist positions without infantry support, but took heavy losses from anti-tank guns (35 to 40 percent of its tanks in some attacks). Nevertheless, the T-26 was used with great success during the Battle of Guadalajara in March 1937 after the 1st Tank Brigade was finally formed (its HQ was in Alcalá de Henares). For example, a platoon of two T-26 tanks under the command of Spaniard, E. Ferrera destroyed or damaged twenty-five Italian tankettes on 10 March 1937. In September/October 1937 the Republican 1st Tank Brigade was disbanded. Some volunteers returned to the USSR, while others joined with the International Tank Regiment under the command of Soviet major S.A. Kondratiev.