 "U-26" headed back through the Straits, arriving in Wilhelshaven on 5 December 1939; the only U-boat to enter and leave the Mediterranean in the war.This mission was summed-up in the BdU "Kriegstagebuch" (KTB) War Diary,

It was a mistake to send "U-25", "U-26" and "U-53" into the Mediterranean.