tons overall. Return to the North Sea At the beginning of 1917, Hersing left the Mediterranean to support the unrestricted submarine warfare campaign of the German Seekriegsleitung. Between 16 and 17 February, Hersing intercepted and sank two British merchant ships and two small Portuguese ones off the Portuguese coast. Four days later, it was the turn of the French freighter Cacique (2,917 tons), sunk in the Bay of Biscay. On February 22, U-21 arrived in the Celtic Sea and finished off the Dutch steamer Bandoeng, already damaged by another German submarine. The same day Hersing sank six more Allied ships, five of them Dutch (the largest of which being Noorderdijk, over 7,000 tons) and one Norwegian (Normanna, 2,900 tons). A seventh ship, Menado suffered severe damage, but avoided sinking. In just one day, Hersing sank a total of seven ships, totalling more than 33,000 tons. Hersing then sailed into North Sea between Scotland and Norway. On April 22, he sunk the steamers Giskö and Theodore William. On April 29 and 30, he sank the Norwegian Askepot and the Russian bark Borrowdale. In the same area, the British steamers Adansi and Killarney suffered the same fate on May 6 and 8, respectively. On June 27, Hersing sank the Swedish auxiliary barge Baltic, carrying a cargo of timber. Hersing's service in command of U-21 ended in September 1918 when, two months before the Armistice of 11 November 1918, he was assigned to the submarine navigation school at Eckernförde as an instructor. During the war. Hersing was responsible for the sinking of 40 ships (36 merchantmen and four warships), for a total of more than 113,000 tons; this made him one of the most successful submarine commanders of the Kaiserliche Marine. After the war After the armistice, Hersing was given responsibility for the withdrawal of German troops from the city of Riga (in present Latvia). It is suspected that he subsequently was involved in the February 1919 sinking of U-21. His former boat was surrendered to the Allies after the end of the war and sank under mysterious circumstances on 22 February 1919, during the transfer to Great Britain, where it should have formally surrendered. In 1920, he was probably involved in the Kapp Putsch, an attempted coup against the newly formed Weimar Republic, but this had no consequences and he remained in the navy. In 1922, he was promoted to Korvettenkapitän (corvette