The German UB II design improved upon the design of the UB I boats, which had been ordered in September 1914.^[4] In service, the UB I boats were found to be too small and too slow. A major problem was that, because they had a single propeller shaft/engine combo, if either component failed, the U-boat became almost totally disabled.^[5] To rectify this flaw, the UB II boats featured twin propeller shafts and twin engines (one shaft for each engine), which also increased the U-boat's top speed.^[6] The new design also included more powerful batteries,^[5] larger torpedo tubes, and a deck gun.^[7] As a UB II boat, U-43 could also carry twice the torpedo load of her UB I counterparts, and nearly ten times as much fuel.^[7] To accommodate all of these changes the boats' had larger hulls,^[5] and surface and submerged displacements more than twice those of the UB I boats.^[7]

The Imperial German Navy ordered UB-43 from AG Weser on 31 July 1915 as one of a series of six UB II boats (numbered from UB-42 to UB-47) UB-43 was 36.90 metres (121 ft 1 in) long and 4.37 metres (14 ft 4 in) abeam. She had a single hull with saddle tanks and had a draft of 3.68 metres (12 ft 1 in) when surfaced. She displaced 305 tonnes (300 long tons) while submerged but only 272 tonnes (268 long tons) on the surface.^[3]

The submarine was equipped with twin Daimler diesel engines and twin Siemens-Schuckert electric motors—for surfaced and submerged running, respectively—that drove one propeller shaft. UB-43 had a surface speed of up to 8.82 knots (16.33 km/h; 10.15 mph) and could go as fast as 6.22 knots (11.52 km/h; 7.16 mph) while underwater. The U-boat could carry up to 27 tonnes (27 long tons) of diesel fuel, giving her a range of 6,940 nautical miles (12,850 km; 7,990 mi) at 5 knots (9.3 km/h; 5.8 mph) Her electric motors and batteries provided a range of 45 nautical miles (83 km; 52 mi) at 4 knots (7.4 km/h; 4.6 mph) while submerged.^[3]

UB-43 was equipped with two 50-centimeter (19.7 in) bow torpedo tubes and could carry four torpedoes. The U-boat was also armed with one 8.8 cm (3.5 in) Uk L/30 deck gun.^[3]

UB-43 was laid down by AG Weser at its Bremen shipyard on 3 September 1915.^[1] As one of six U-boats selected for service in the Mediterranean while under construction, UB-43 was broken into railcar-sized components and shipped overland to the Austro-Hungarian port of Pola.^[8][9] Shipyard workers from Weser assembled the boat and her five sisters at Pola,^[8] where she was launched on 8 April.^[1]

SM UB-43 was commissioned into the German Imperial Navy on 24 April 1916 under the command of Oberleutnant zur See Dietrich Niebuhr;^{[1][Note 1]} UB-43 was the only U-boat command for the 27-year-old officer.^[10] UB-43 was assigned to the Navy's Pola Flotilla (German: Deutsche U-Halbflotille Pola) in which she remained throughout her German career.^[1] Although the flotilla was based in Pola, the site of the main Austro-Hungarian Navy base, boats of the flotilla operated out of the Austro-Hungarian base at Cattaro which was located farther south and closer to the Mediterranean. German U-boats typically returned to Pola only for repairs.^[11]

Under Niebuhr's command, UB-43 had no success,^[10] and he was replaced by Kapitänleutnant Hans-Joachim von Mellenthin on 29 August.^[1] After two weeks under von Mellenthin's command, UB-43 sank her first ship. While 112 nautical miles (207 km; 129 mi) east of Malta, the British steamer Italiana with her cargo of hay destined for Salonica was torpedoed and sunk.^[12] Three days later, and some 60 nautical miles (110 km; 69 mi) closer to Malta, von Mellenthin sank a pair of British steamers. Dewa was in ballast headed for Port Said when attacked by UB-43; three of the steamer's crew lost their lives in the attack.^[13] Lord Tredegar was carrying a general cargo when she was sent down with the loss of four men.^[14] The Wall Street Journal reported that the sinking of Lord Tredegar resulted in a loss of $1,000,000 for her American insurer.^[15]

In October, von Mellenthin and UB-43 sank an additional two ships.^[16] On 10 October, the British tanker Elax, carrying fuel oil from Rangoon was sunk off Cape Matapan without casualties.^[17] Three days later, two men were killed when UB-43 torpedoed and sank their ship, the British steamer Welsh Prince, of 4,934 gross register tons (GRT).^[18]

On 18 November, the British Admiralty, released a report that listed all of UB-43's first five victims as evidence of German wrongdoing. According to the British report, Italiana, Dewa, Lord Tredegar, and Elax—four of the twenty-two ships listed—had all been torpedoed without warning. This type of attack was counter to German pledges to adhere cruiser warfare, which required that ships be allowed time for the crews to escape before any attack could commence.^[19] UB-43's fifth victim, Welsh Prince, was on another list of 107 British ships sunk whose lifeboats had been fired upon by German submarines.^[19]

In the meantime, UB-43 had continued sinking British ships, sending down five in a nine-day span in early November.^[16] Statesman, a 6,153 GRT steamer carrying a general cargo, was first on 3 November; six crewmen were killed when the ship went down 200 nautical miles (370 km; 230 mi) east of Malta.^[20] The following day, the 3,937 GRT Clan Leslie and the 5,398 GRT Huntsvale were sunk in the same area.^[21][22] Clan Leslie was carrying a general cargo from Bombay when sunk with three casualties.^[21] Seven were killed when Huntsvale, traveling in ballast for Algiers, was sunk.^[22]

On 6 November, UB-43 torpedoed the Peninsular and Oriental liner Arabia 112 nautical miles (207 km; 129 mi) off Cape Matapan.^[23] According to contemporary news accounts, gunners on Arabia fired upon UB-43 after the liner was torpedoed, but recorded no hits.^[24] All 437 passengers aboard the steamer,^[25] en route from Sydney to London when attacked,^[23] were rescued after an hour in the water. The liner went down 90 minutes after the torpedo struck. Eleven died in the attack,^[26] including two of Arabia's engineers killed in the initial blast of the torpedo.^[24] Six days after Arabia's sinking, UB-43 sank the 3,383 GRT British steamer Kapunda east of Malta.^[27] Kapunda's loss brought the U-boat's November tally to 26,774 gross register tons,^[16] which accounted for more than 15% of the November tally for all German U-boats in the Mediterranean.^[28]

UB-43 and von Mellenthin sank three more British steamers in December: Bretwalda on the 13th, and Russian and Westminster on the 14th.^[16] Bretwalda—which had escaped destruction from a mine laid by UC-5 in August 1915—and her cargo of jute were sent down 220 nautical miles (410 km; 250 mi) from Malta.^[29] Russian, at 8,825 GRT, was the largest ship sunk by UB-43;^[16] the horse transport ship was sailing in ballast from Salonica when she went down with 28 of her crewmen.^[30][31] After UB-43 torpedoed Westminster,^[16] the U-boat shelled the survivors in their lifeboats, according to authors R. H. Gibson and Maurice Prendergast.^[30] Fifteen men from Westminster died in the sinking.^[32]

UB-43 sank no ships over the next eight weeks.^[16] Author Paul Halpern reports that the majority of the German U-boats in the Mediterranean fleet were undergoing repairs and refits at Pola and Cattaro during January. Although no specific mention is made of repairs done on UB-43, the U-boat's inactivity in this period may be for that reason.^[33]

Unrestricted submarine warfare edit

On 1 February 1917, Kaiser Wilhelm II personally approved a resumption of unrestricted submarine warfare in order to try to force the British to make peace.^[34] The new rules of engagement specified that no ship was to be left afloat,^{[35][Note 2]} although British reports for several of UB-43's victims suggest that von Mellenthin was already operating in this manner.^[25]

Under these new rules of engagement, UB-43 first sank the Greek steamer Miaoulis 130 nautical miles (240 km; 150 mi) from Benghazi on 24 February, while she was carrying cottonseed to London.^[36][37] Two days later, the turret hull steamer Clan Farquhar,^[38] carrying cotton and coal for London,^[37] was torpedoed and sunk. After the attack, which killed 49 of her crew, the ship's second engineer was taken captive by von Mellenthin.^[38] On the 27th, Brodmore and her cargo of frozen meat from Majunga were sunk off Libya (and her master taken prisoner),^[39] and on the 28th the Japanese steamer Shinsei Maru was sunk nearby.^[40]

She was nearly a month later before von Mellenthin and UB-43 sank their next target. On 26 March, the British steamer Ledbury, carrying wheat from Karachi, was sunk 90 nautical miles (170 km; 100 mi) from Benghazi.^[41] Eight days later, Vasilefs Constantinos, a Greek steamer of 4,070 gross register tons (GRT), was sunk in the Ionian Sea; the Constantinos was the last ship sunk by UB-43 under von Mellenthin's command.^[42] On 9 April, von Mellenthin was succeeded by Oblt.z.S. Horst Obermüller,^[1] a 26-year-old first time U-boat commander.^[43] Under von Mellenthin's command, UB-43 had sunk 86,236 gross register tons (GRT) of merchant shipping.^{[Note 3]}

On 1 May, Obermüller sank the American-owned (but British-flagged) tanker British Sun carrying a load of fuel oil.^[44] According to a report in The New York Times, the 5,565 GRT vessel, valued at $2,500,000, was "one of the finest" tankers.^[44][45] The collier Repton was sent down off Cape Matapan six days later; three of the British steamer's crewmen died in the attack.^[46] Later in the month, the Greek steamer Dorothy and her cargo of wheat from Karachi were sunk 45 nautical miles (83 km; 52 mi) from Cap D'Armi.^[47] UB-43's final attack of note was upon the protected cruiser HMS Grafton, torpedoed 150 nautical miles (280 km; 170 mi) east of Malta. Grafton was damaged but suffered no casualties.^[48] The 7,350-tonne (7,230-long-ton)-displacement British ship was brought safely into port at Malta.^[49]

On 21 July, UB-43 was decommissioned at Pola and handed over to the Austro-Hungarian Navy. In her German Imperial Navy career of fourteen months, UB-43 sank twenty-two merchant ships totaling 99,176 gross register tons (GRT), and damaged one warship with a displacement of 7,350 tonnes (7,230 long tons).^{[1][Note 4]}

In November 1916, the German Imperial Navy, having a hard time finding trained submarine crews, inquired to find out if its ally Austria-Hungary was interested in purchasing some of its Mediterranean submarines. A general agreement led to protracted negotiations, which stalled over the outflow of Austro-Hungarian gold reserves to Germany. But, with all of the details worked out, the two parties agreed on the sale of UB-43 and sister ship UB-47 to Austria-Hungary in June 1917.^{[50][Note 5]}

When handed over by the Germans on 21 July, UB-43 was in a "worn out condition". Despite the rough condition of the boat, the U-boat was commissioned into the Austro-Hungarian Navy on 30 July 1917 as SM U-43, dropping the B from her former designation. Linienschiffsleutnant Friedrich Schlosser was installed as the new commander of the U-boat,^[2] which remained at Pola for the next three months undergoing repairs. Departing that port on 1 November, U-43 made way to Cattaro, and then went out on patrol.^[51] Schlosser torpedoed the Italian steamer Orione on 16 November, but the Italian ship did not sink; she was towed to safety in Taranto.^[52]

On 30 November, a leak on U-43 partially flooded the boat and caused her to sink to a depth of 100 metres (330 ft) before she was brought under control and raised to the surface. The flooding damaged the U-boat's electrical systems, preventing her from submerging on her return to port for repairs. An unidentified submarine launched a torpedo at the surfaced U-43, but the torpedo's aim was off and it passed harmlessly in front of the bow. The boat made port at Cattaro on 1 December and at Pola on 6 December for two months of repairs.^[51]

During U-43's time under repair, Schlosser was reassigned to command U-14,^[53] and Linienschiffsleutnant Eugen Hornyák Edler von Horn was named to take his place aboard U-43 on 18 January 1918.^[2][54] Under von Horn, U-43 patrolled off Cattaro, having to crash dive at least once to escape attack from enemy torpedo boats. On 17 March, while returning to Cattaro from patrol, the crew of the Austro-Hungarian destroyer Dinara mistook U-43 for an enemy submarine and rammed her, damaging the diving planes. U-43 sailed for Fiume for three months of repairs.^[51]

The U-boat returned to action in June and patrolled off Montenegro, Durazzo, and Cattaro for the next five months. On 13 June, U-43 was slightly damaged in an air raid on Cattaro and, on 5 September, had to crash dive to avoid another air attack while off Cattaro. On 20 September, the boat rendezvoused with U-47 and received a French prisoner of war. The prisoner was the only survivor of the French submarine Circé, which U-47 had torpedoed the night before.^[51]

At the end of the war, U-43 was at Cattaro.^[55] In her Austro-Hungarian Navy career, U-43 damaged a single merchant ship of 4,016 gross register tons.^[2] U-43 was ceded to France as a war reparation in 1920, towed to Bizerta, and broken up there within a year.^[55]

As the German UB-43 edit

As the Austro-Hungarian U-43 edit