 The Kriegsmarine had acquired some knowledge of the area; Dönitz was an officer aboard "UB-68" which had been sunk in the region in World War I. U-boats had also served in the Spanish Civil War.The Republicans, with twelve submarines, opposed the Nationalists, who had none; the presence of German U-boats was most welcome.The first two vessels, "U-33" and "U-34", under the codename "Training Exercise Ursula", left Wilhelmshaven on 20 November 1936.