For the German military of World War 2 (1939-1945), victory was not only to be had on land and in the air but also on the sea. Its fighting forces relied heavily on convoys crossing the northern reaches and in the Mediterranean Theater and, as such, vessels of many types were developed to support such operations - one design becoming the "R-Boot" ("Raumboote") class of motor torpedo boats.
Like the related "S-Boot" family (detailed elsewhere on this site), R-Boots were designed and developed during the interwar years preceding World War 2. Unlike other warships, the type was not restricted by the Versailles Treaty signed by Germany after the war. The R-Boot was designed as a smaller companion to the larger S-Boots and developed around the need for coastal minesweeping services.
The original batch of boats was built from the late-1920s into the early-1930s and covered hull numbers R1 through R-16. These displaced 60 tons (long) and sported 26 meter overall lengths. Builders included Lurssen, Bremen-Vegesack, Travemune and others with the last boat arriving in 1934. From 1934 until 1938, the next batch covered hull numbers R17 to R24 and had their displacement and lengths increased to 115 tons and 37 meters respectively (their beams were also increased as a result). R25 through R40 arrived from 1938 to 1939 and were slightly lighter (110 tons) and shorter (35.4 meters). R41 through R129 managed displacements of 125 tons and lengths of 37.8 meters, being built until 1943. From there arrived R130 to R150 which showcased a displacement of 150 tons and a length of 41 meters - these constructed up until 1944.
Back in 1940, R151 through R217 began construction and these ranged into 1943, carrying a displacement of 125 tons and length of 35.4 meters. 1943 saw the beginning of R218 to R300 of 140 tons and 39.2 meter lengths - though R291 through R300 remained unfinished before the end of the war in 1945. R301 through R312 appeared as 160-ton vessels with 41 meter lengths and were constructed from 1942 until 1945 - the primary change being 2 x 533mm torpedo tubes added for offensive-minded ship-hunting sorties. R401 through R448 were the last of the R-Boot classes and were 140-ton vessels with 39.2 meter lengths. While launched from 1943 until 1945, most of the group were not finished before the end of the war.
As designed these boats were sleek and carried low profiles. Their draughts were deliberately shallow so as to operate effectively along coastlines and, due to their intended mission scope, were only modestly-armed through a sole turreted 37mm C/30 series cannon facing aft and between two and six 20mm cannons. 7.92mm machine guns were also fitted for extremely close-in defense. For minelaying duties, the boats were outfitted with mine and depth charge dispensers and only the aforementioned class of R301-R312 boats carried torpedo launchers (2x).
The operating crew numbered as many as thirty-eight personnel while propulsion power was derived from 2 x MAN marine diesels outputting 1,836 horsepower each and driving 2 x shafts under stern. The boats could made headway at seventeen knots though the torpedo-equipped R301-R312 carried triple-screw propulsion for speeds reaching 24 knots. Some were outfitted with Voith-Schneider propeller units for increased maneuverability. Construction involved a metal understructure with wood framing with rounded bilges built-in.
Despite the original intent to feature these boats as minesweepers, the line was employed in all manner of roles for the German Navy as wartime needs required - these to include Search and Rescue (SAR), ship hunting, coastal patrolling and general convoy escort to name a few- as it stood, the boats rarely operated in their intended minesweeping roles, such was the nature of the war for the German Navy. They proved critical components in the German operation against Norway in 1940 and a total of 424 boats were ultimately completed, seeing service everywhere the Navy operated and well into the final weeks of the war in 1945.
Despite their numbers, many were lost for just 140 survived the conflict and the Allies managed to capture stocks of the type before the end. With the war over, the boats became spoils of war and were disbursed among some of the conquerors though about 24 were eventually reintroduced in the post-war West German Navy and operated until their usefulness had run out in the 1960s.