The Hrabri class consisted of two submarines built for the Kingdom of Serbs, Croats and Slovenes (later Yugoslavia) by the Vickers-Armstrong Naval Yard, on the River Tyne, in the United Kingdom. Launched in 1927, the vessels were named Hrabri (Brave) and Nebojša (Fearless). Their design was based on that of the British L-class submarine of World War I, and they were built using parts originally assembled for L-class submarines that were never completed. The Hrabri-class were the first submarines to serve in the Royal Yugoslav Navy, and the class was joined by the two smaller French-made Osvetnik-class submarines to make up the pre-war Yugoslav submarine force. They were armed with six bow-mounted 533 mm (21 in) torpedo tubes, two 102 mm (4 in) deck guns and one machine gun, and could dive