The five destroyers carried out patrols to defend Portugal's neutrality during the Second World War. Their anti-aircraft armament was revised during 1942–43, with the three pom-poms and one of the banks of torpedo tubes replaced by six 20 mm cannon. They were refitted by Yarrow from 1946–49, with the machinery refurbished, anti-aircraft armament again revised to three Bofors 40 mm gun in powered mounts and three 20 mm cannon, and sonar and radar (British Type 285 and Type 291) fitted. Douro reached a speed of at during post-refit trials.
