The action of 14 October was a naval engagement of the First World War when the Imperial German Navy submarine SM U-139 attacked the Portuguese civilian steamer São Miguel and the Portuguese Navy naval trawler NRP Augusto de Castilho in the Atlantic Ocean on 14 October 1918.

[1] On the island of Madeira, the Portuguese patrol boat NRP Augusto de Castilho under the command of the First Lieutenant Carvalho Araújo received the mission of escorting the Portuguese civilian steamer São Miguel, which was property of the Empresa Insulana de Navegação and was sailing from the Port of Funchal in Madeira to the port of Ponta Delgada on the Azores archipelago, with 206 passengers and several tons of cargo on board.

[3] After leaving Funchal at sunset on 13 October, São Miguel came under fire at 06:15 AM on 14 October from the German submarine U-139, one of the more and better equipped submarines of the Imperial German Navy, armed with two powerful 150 mm cannon and six torpedo tubes, and under the command of Lothar von Arnauld de la Perière.

In order to protect São Miguel, and after using all the smoke canisters available for creating a smoke curtain while repeatedly firing the stern cannon, Araújo gave orders for NRP Augusto de Castilho to turn to port, describing half a circle, and advance towards the German U-139, taking gunfire from the submarine, thus giving São Miguel time to escape at full speed.

However, the German submarine continued firing, hitting the patrol ship with a direct shot which killed Araújo and injured Midshipman Armando Ferraz for a second time.