In late 1757 Osborn besieged the neutral port of Cartagena in Spain where a French squadron designed to go to the relief of Louisbourg had taken shelter. While there he attacked a small French squadron under Michel-Ange Duquesne de Menneville which was coming to the aid of the trapped force. Two French ships were captured, including Duquesne's flagship and it indirectly led to the successful British capture of Louisbourg later that year. The battle helped to restore the Royal Navy's reputation following the failed attempt to relieve Minorca two years earlier which had led to Admiral Byng's execution.