Complex sentence: On 25 April, the entrance of Cárdenas' port was being patrolled by the "Ligera" under Lieutenant Antonio Pérez Rendón, an experienced Cádiz-born officer who had seen action against the Cuban insurgents many times during the war.
Split into simpler sentences: On 25 April, the "Ligera" patrolled the entrance of Cárdenas' port. Her commander was Lieutenant Antonio Pérez Rendón, an experienced Cádiz-born officer who had seen action against the Cuban insurgents many times during the war.