Although the first references are from the 15th century, when both Hussites and Crusaders are said to have used rockets during the Hussite Wars (also known as the Bohemian Wars), there is no strong evidence that rockets were actually used at that time. It is worth noting that Konrad Kyeser, who described several rockets in his Bellifortis manuscript, written 1402-1405, served as advisor to Bohemian King Wenceslas IV. Rockets were, in fact, used as fireworks from the 16th century in noble circles. Some of these were built by Vavrinec Kricka z Bitysky, who also published a book on fireworks, in which he described how to build rockets for firework displays. Czech soldiers were also involved in the creation of a rocket regiment in the Austrian (Austro-Hungarian) Army in the first half of the 19th century. The pioneering era of modern rocket development began in the Czech lands during the 1920s. The first rockets were successfully launched by Ludvik Ocenasek in 1930, with one of them possibly reaching an altitude of 2,000 m. Vladimir Mandl, lawyer and author of the first book on the subject of space law, patented his project for a multistage rocket (vysokostoupajici raketa) in 1932, but this project never came to fruition. There were several factories during the so-called Protectorate of Bohemia and Moravia in 1939-1945, when the Czech lands were occupied by Nazi Germany, where parts for German A-4/V-2 rockets were produced, but none of the Czech technicians or constructors was able to build an entire rocket. The main goal of the Czech aviation industry after World War II was to revive the stagnant aircraft industry. There was no place to create a rocket industry. Interest in a rocket industry appeared at the end of the 1950s. The Political Board of the Central Committee of the Czechoslovak Communist Party started to study the possibilities of creating a rocket industry after the first flight into space, and particularly after U.S. nuclear weapons were based in Italy and West Germany in 1957 and 1959. The first project involved the meteorological rockets Sokol I and Sokol II in 1960, which were never completed, as the rocket industry and rocket development came under the exclusive sphere of interest of the Soviet Union. In Czechoslovakia a Rocket Research and Test Institute was created by the Czechoslovak Ministry of Defence in 1963. The first Czechoslovak rockets to find practical use were launched in 1965.