 Mazarredo achieved his greatest military success as Cordova's chief of staff.Thanks to his proposal of a bold manoeuvre, which his colleagues considered reckless, Cordova's fleet of 31 ships of the line and 6 frigates overcame a British convoy of 63 merchant ships escorted by a ship of the line and 2 frigates in the Action of 9 August 1780.55 British merchant ships were captured, including 5 East Indiamen.