The De Schelde shipyard was one of the largest shipbuilding facilities in the Netherlands. The yard handled both civilian and military contracts and was among the country’s most important centres for naval construction - a position it would retain for many years thereafter.
The Germans shared the Dutch appreciation of the yard’s strategic value and had no intention whatsoever of damaging the facility. On the contrary, it was considered far too valuable for their own plans in the near future.
The shipyard is still in use today, albeit as part of the large Dutch shipbuilding company Damen Shipyards.
In May 1940, De Schelde was working on a considerable number of naval contracts at various stages of completion. Among them were two large destroyers - the HrMs Isaac Sweers and the HrMs Philips van Almonde (1) - Dutch-designed vessels of 2,240 tons displacement that were conceived as a heavy destroyer. The Isaac Sweers had already been launched and commissioned, whereas the Philips van Almonde had not yet reached that stage. The yard was also constructing two highly modern submarines, the O21 and the O22. Both vessels had already been commissioned and were seaworthy, but neither had yet completed its diving trials - an essential process for ensuring that all valves and gaskets were fully watertight
(1) These large destroyers had been desigend in a class of four ships. They were 107 m long with a top speed of 36 knots. Armament would comprise five 12 cm Bofors guns [two twin mounts, one single], four 40 mm Bofors AA guns, four 12,7 mm AA machineguns and eight 53,3 cm torpedo tubes. Additionally 24 mines on a dual rail system, four depth charges mortars and facility for one sea-plane. The armament of the actually launched ships that would later serve in the Royal Navy - under Dutch flag - was altered. The two other ships of this class were commissioned by Rotterdamse Droogdok Maatschappij [RDM] in Rotterdam. Of those two, one was commissioned by the Kriegsmarine and sunk by Allied destroyers on June 9, 1944 as ZH-1.
As early as the morning of 10 May, it was decided that the vessels under construction at De Schelde yard had to be kept out of German hands. Plans were therefore made to tow all four ships to England. It soon became clear, however, that the HrMs Philips van Almonde was not sufficiently seaworthy to endure the passage under tow, whereas the other three vessels were capable of making the journey. Consequently, the Philips van Almonde was scuttled by a demolition party on the morning of 17 May, although the Germans would later salvage the hull.
The HrMs Isaac Sweers was towed from the dockyard at Flushing to England later that same evening by the tug navy HrMs Zwarte Zee. In the United Kingdom, the destroyer was completed and re-equipped at the Thornycroft Dockyard in Southampton with new armament and radar systems. Its revised armament consisted of six 102 mm guns, four 40 mm Bofors anti-aircraft guns, four 20 mm Oerlikon anti-aircraft guns, and eight 533 mm torpedo tubes.
Both submarines, which were already capable of operating under their own power, departed under the escort of the auxiliary vessel BV-37 (HrMs Schelde), a tug armed with a multipurpose 50 mm gun. All three vessels reached the United Kingdom safely, where they received a warm welcome.
The HrMs Isaac Sweers was commissioned into the Royal Navy later in 1940, though she continued to be manned largely by a Dutch crew. During her service she participated in several naval engagements, the most notable being the Battle of Cape Bon in December 1941. She was also present during the loss of the aircraft carrier HMS Ark Royal, which was torpedoed by a German U-boat in November 1941.
During the Battle of Cape Bon on 13 December 1941, the Isaac Sweers served as part of the 4th Destroyer Flotilla under Commander Stokes. Together with the British destroyers HMS Sikh, HMS Legion, and HMS Maori, she contributed to the sinking of the Italian light cruisers IS Alberico da Barbiano and IS Alberto di Giussano, both displacing approximately 6,570 tons, the latter being the lead ship of her class. During the same action, the Dutch destroyer also damaged the Italian torpedo-boat IS Cigno.
The fate of the Isaac Sweers, however, would ultimately be tragic. During the Allied landings in North Africa, she was struck by two torpedoes fired by the German submarine U-431 off the coast of Algiers on 13 November 1942. Of her crew of 194 men, only 86 survived.
The O21-class submarines — comprising the O21 through O27 — were among the most modern submarines of their time. The O21 and O22 were even equipped with snorkel systems that allowed batteries to be recharged while submerged at periscope depth, a concept later adopted by the German U-boat fleet. Curiously, the Royal Navy initially disapproved of the system and had it removed. The submarines had a maximum speed of 20 knots surfaced and 9 knots submerged, a diving depth of 175 metres, and were armed with four 21-inch torpedo tubes. They also carried an 88 mm deck gun, a 40 mm Bofors anti-aircraft gun, and a 12.7 mm Vickers anti-aircraft machine gun.
The O21 through O24 were evacuated to the United Kingdom and subsequently served under the Dutch naval ensign alongside the Royal Navy. The O25 through O27, however, were captured and commissioned into the German Kriegsmarine.
The Dutch submarines were organised into a small Dutch submarine flotilla operating within the Royal Navy. Soon after the fall of the Netherlands, these modern boats began war patrols from British ports, and by 30 June 1940 they had commenced operations in Norwegian waters, crewed entirely by Dutch personnel. The first major loss to strike this modest Dutch submarine force came in November 1940, when the O22 disappeared with all hands - 43 Dutch and 3 British crew members - during a patrol off Norway. The cause of her loss remains unknown to this day. In 1993, the wreck was discovered some 100 kilometres off the south-western Norwegian coast and examined by remotely operated vehicles. No visible signs of damage were found, leaving the mystery unresolved.
In the autumn of 1940, the O21 was assigned patrol duties in the North Sea and Norwegian waters before later being transferred to Gibraltar, which became her new base of operations. She subsequently operated in the Mediterranean, where on 29 November 1941 she achieved considerable fame by sinking the German submarine U-95. The event was celebrated throughout the Allied navies, as it marked the first successful submarine-versus-submarine kill by an Allied submarine during the height of the Kriegsmarine's U-boat campaign. When the surviving German crew members rescued by the O21 were landed at Gibraltar, Allied ships in the harbour saluted the Dutch submarine in tribute.
The O21 became the most successful Dutch naval vessel of the war, sinking more than 13 German, Italian, and Japanese ships while surviving the conflict intact. She remained in service until being decommissioned in 1957. Her sister ships O23 and O24 also survived the war and were decommissioned in 1948 and 1954 respectively.