Z39 was a Type 1936A (Mob) destroyer built for Germany's Kriegsmarine during World War II. She was laid down in August 1940 and completed three years later. Her anti-aircraft armament was increased extensively during the war. Z39 served with the 6th Destroyer Flotilla her entire German career, which she spent escorting transports in the Baltic Sea, laying mines, and bombarding land forces. The destroyer served the navies of a total of three different countries: from 1943 to 1945 with the Kriegsmarine as Z39, from 1945 to 1947 with the United States Navy as DD-939, and from 1948 to 1964 with the French Navy as Q-128.
Throughout her German service, the ship laid numerous barrages (explosives concentrated over a wide area) of mines in the Baltic Sea and bombarded Soviet forces several times. In the last months of the war, Z39 helped escort steamships that were evacuating German soldiers and civilians from Eastern Europe to Denmark. Z39 was damaged twice, once by Soviet planes while in Paldiski and then by British planes while in Kiel. At the end of the war, the destroyer was transferred to the United States Navy. It conducted experiments testing her equipment—her high-pressure steam propulsion plant in particular. After the US Navy deemed her obsolete, the ship was transferred to the French Navy, where she was cannibalized for parts, and made into a pontoon boat for minesweepers.
Background Interbellum Following the end of World War I Germany signed the Treaty of Versailles, which put strict limits both on the size and displacement of warships that she could possess. During the Interbellum, the period between the first and second world wars, the average size of Allied ships and their armaments in almost all warship categories grew substantially. As a result of the treaty, Germany felt that her ships could not compete with those of the Allied navies and began to ignore the treaty, at first covertly, and later openly after Hitler, the (dictator) of Nazi Germany, publicly denounced it in March 1935. The displacements of all German ships at the time were purposefully understated to have their official sizes comply with the treaty. At first, these changes were made with the goal of being able to match or exceed French and Polish destroyers, but later it was necessary that these destroyers be able to match British destroyers, a much more difficult goal.
Due to the comparatively small number of German shipyards, compared to the British or French, Germany adopted a policy of over-arming her destroyers to compensate for their low numbers, so that they bore similar armament to French and Polish light cruisers. Several negative consequences resulted from this, such as making them slower and overweight. Although German heavy destroyers matched British light cruisers in armament, they were much less seaworthy and had far worse facilities for control and use of their guns.
Plan Z Plan Z was a German naval rearmament plan that started in 1939, and involved building ten battleships, four aircraft carriers, twelve battlecruisers, three pocket battleships, five heavy cruisers, forty-four light cruisers, sixty-eight destroyers, and 249 submarines. These ships were to form two battle fleets: a "Home Fleet" to tie down the British war fleet in the North Sea, and a "Raiding Fleet" to wage war upon British convoys. Erich Raeder, the Grand Admiral of the Kriegsmarine, was assured by Hitler that war would not start until at least 1945. Raeder had wanted the deadline for the completion of Plan Z to be extended to 1948, but Hitler insisted on 1945, although Hitler privately wanted to be at war with the Anglo-French alliance by 1942. World War II began in 1939, meaning that very few of Germany's heavy ships would be finished at that point. Germany's main naval opponents were France and England. Compared to the number of ships Germany had upon entry into the war (in parentheses) they had: 22 battleships (two), seven carriers (none), 22 heavy cruisers (four), 61 light cruisers (six), 255 destroyers (34), 135 submarines (57, of which less than half could actually serve in the Atlantic or the North Sea). Due to the clear advantage her enemies had, Raeder remarked that the Kriegsmarine could not hope to win, and thus the only course for them was to "die valiantly".
Destroyer function The function of the destroyer was defined by its evolution: around the 1870s, nations that could not directly threaten Great Britain's navy began to invest in torpedo boats, small and agile ships which used their torpedoes to deliver enough damage to pose a tactical issue to enemy fleets. Near the turn of the 20th century, British and German torpedo boats grew in size to the point of creating a separate line of sea-going torpedo craft, "torpedo boat destroyers", or simply destroyers, designed in part to counter torpedo boats themselves. Experience in World War I showed that destroyers very rarely engaged capital ships, but more often fought other destroyers and submarines; because of this, destroyers were partially re-focused towards escort and anti-submarine services. During the war, they were used as "maids of all work", fulfilling virtually every role to some degree, and, unlike capital ships, which rarely left port during the war, served in numerous operations. By the end of the war, destroyers were perceived as one of the most useful classes of ships.
During World War II, destroyers served essentially the three basic functions they had in World War I: to act as screening ships to defend their fleets from those of an enemy, to attack an enemy's screening ships, and to defend their fleet from submarines. However, there was an increased desire to introduce anti-aircraft measures to the destroyers, although many nations struggled to do so effectively. How destroyers were actually used varied by country. Germany did not use her destroyers to defend against submarines, hence their lack of strong anti-submarine armament. Germany relied on a massive fleet of trawlers that had been requisitioned and refitted as minelayers instead. British destroyers were built for escorting fleets, defending them from enemy planes and sinking submarines. German destroyers were built to escort fleets, or act as torpedo boats. The role of the destroyer began to vary more widely as World War II progressed, with five parallel evolutions: the all-purpose destroyer (all countries), the anti-submarine destroyer (United States and United Kingdom), the anti-aircraft destroyer (Japan and the United Kingdom), the small destroyer (Germany and Italy), and the super-large destroyer (France).
Design and armament Z39 was of the Type 1936A (Mob) destroyer class. She was long at the waterline and long overall, had a beam of , and a draught of . The destroyer had a displacement of at standard load, and at full load. Her crew complement was 332.
Before Project Barbara modifications to improve the anti-aircraft capabilities of German ships, the ship was armed with: seven anti-aircraft (AA) guns, two twin 3.7 cm SK C/30 anti-aircraft guns, a twin L/48 gun on a forward turret, two single L/48 guns in a gunhouse aft, two quadruple torpedo tubes, and 60 mines. Z39 had the Greek coat of arms on either side of her twin turret. After the modifications, the destroyer carried eighteen and fourteen twin guns; the rest of her armament remained unchanged.
Her propulsion system consisted of six Wagner water-tube boilers that generated and fed high-pressure superheated steam (at and ) to two sets of Wagner geared steam turbines. These gave the ship a rated power of , and a top speed of . She had a range of , at her cruising speed of .
Z39s sensor suite housing included a FuMO 21 radar that was placed on the ship's bridge and four FuMB4 Sumatra aerials on the foremast searchlights. The ship also had several other radars and radar detectors, including a FuMB 3 Bali and FuMO 81 Berlin-S on her masthead and a FuMO 63 Hohentweil K. She also had a degaussing cable that wrapped around the entire ship, but was covered by her spray deflector.
Service history Z39 was ordered on 26 June 1939, laid down by Germaniawerft at Yard G629 in Kiel on 15 August 1940, launched on 2 December 1941 and was commissioned on 21 August 1943. Her commissioning had been delayed by lengthy construction times, and Z39 was not fully operational until 7 January 1944. There were a number of reasons for these construction issues. The small number of German shipyards forced the Kriegsmarine to prioritize construction, inexperienced naval engineers, and the lack of workers. At some point between her launching and commissioning, she was modified under Project Barbara, with the addition of three pairs of anti-aircraft guns, one pair forward of her bridge, one pair abreast after her funnel, and one pair abreast forward of her funnel. The ship had one pair of single guns added to her after funnel platform. The destroyer had a pair of twin guns added to her bridge wings. She had a pair of quadruple guns and a pair of single guns added to an extended deckhouse at the No. 3 gun position. After her commissioning, the ship began minelaying operations in the Skagerrak and the Kattegat until March 1944 when she was transferred to Reval off the Gulf of Finland.
German service
After the move to Reval, she served in the 6th Destroyer Flotilla, alongside the German destroyers , , and . Between 12 and 13 February Z39 laid mines in the "Dorothea A" barrage, along with two other destroyers and three minelayers. On 10 March, she took part in minelaying operations along with two other destroyers. Between 11 and 12 March, she bombarded Soviet forces near Narva-Jõesuu. From 13 March to 22 April, the destroyer took part in six different minelaying operations. One such operation lasted from 13 to 14 April, in which Z39, two other destroyers, and six minelayers laid the "Seeigel 6b" mine barrage south of Suur Tytärsaari. From 16 to 17 April, Z39, two other destroyers, and six minelayers laid the "Seeigel 3b" barrage off of Vigrund Island in Narva Bay. A smokescreen was laid during the operation to prevent the ships from being shelled by Soviet coastal artillery. An operation from 21 to 22 April, involving Z39, two other destroyers, and six minelayers was canceled midway after one of the minelayers hit a mine and sank. From 23 to 24 April, Z39, two other destroyers and eight minelayers laid the "Seeigel 7b/3" barrage in Narva Bay. From 25 to 26 April Z39, two other destroyers and nine minelayers laid the "Seeigel 8b" barrage southwest of Suur Tyärsaari. During the operations between 13 and 26 April, a total of 2,831 mines and 1,174 sweep detonators were laid.