Romero Giménez headed of the 6th Division of the Republican Armed Forces From 1 May 1937, when Alzugaray left its command vacant. On July 1, he was placed in command of the Second Army Corps, which defended the outskirts of Madrid. He participated in the Battle of Brunete, although the performance of his unit was poor in the district of Usera. As commander of the Second Army Corps, he said, regarding forced recruitments that morale in his troops remained good amongst experienced militants but poor amongst recruits, due to their "complete ignorance of the reasons why we fight and a lack of citizen preparedness and desire for freedom".