According to Copeman, Nathan performed well during the Battle of Jarama in February, one of the most heated contests of the Spanish Civil War. Particularly on the third day, he is claimed to have been the most capable officer of the XV International Brigade. During this battle, the Brigade lost more than half of their men; 375 out of 600 died; including Christopher Caudwell. Nathan finally came unstuck at the Battle of Brunete where he was killed as a result of bomb fragments from a Junkers Ju 88 aerial bombardment and died on the 17 July 1937. Romantic myth claims he was "buried under olive trees close to the River Guadarrama," but he was actually buried in the village cemetery of Torrelodones, which was along the way on an evacuation route for the combat wounded and dead from Brunete to Madrid.