Hennig skipped a year, and graduated on 26 February 1932. As early as 1931, Willi Hennig composed an essay entitled Die Stellung der Systematik in der Zoologie ("The state of systematics in zoology") as part of his school work, published posthumously in 1978. It showed his interest as well as his deliberate treatment of systematic problems. Besides school, Hennig worked as a volunteer at the museum and, in collaboration with Meise, saw to the systematic and biogeographical investigation of the "flying" snakes of the genus Dendrophis that became his first published work. From the summer semester of 1932 onwards, Hennig read zoology, botany and geology at the University of Leipzig. He would continue to visit the Museum in Dresden. There, he met the curator of the entomological collection, the Dipteran expert Fritz Isidor van Emden. Hennig saw him regularly until van Emden was expelled from National Socialist Germany for having a Jewish mother and wife. Hennig developed a deep friendship with Emden's successor, Klaus Günther. Hennig concluded his studies with a dissertation entitled, . By this time, Hennig had published eight scientific papers. Besides his 300-page revision of the Tylidae (now classed as Micropezidae), there were further papers on Diptera and the agamid genus Draco of gliding lizards. After his studies, Hennig was Volontär at the State Museum for Zoology in Dresden. On 1 January 1937, he obtained a scholarship from the Deutsche Forschungsgemeinschaft (DFG) to work at the German Entomological Institute of the Kaiser-Wilhelm-Gesellschaft in Berlin-Dahlem. On 13 May 1939, Hennig married his former fellow student Irma Wehnert. By 1945, they had three sons, Wolfgang (born 1941), Bernd (born 1943) and Gerd (born 1945). As a military entomologist Willi Hennig was drafted in 1938 to train for the infantry and concluded this course in 1939. As of the start of World War II, he was deployed in the infantry in Poland, France, Denmark and Russia. He was injured by grenade shrapnel in 1942 and was subsequently used as entomologist at the Institute for Tropical Medicine and Hygiene in Berlin, carrying the rank of a Sonderführer (Z). Just before the war ended, he was sent to Italy to the 10th Army, Heeresgruppe C, to fight malaria and other epidemic diseases. At the end of the war in May 1945, he was captured by the British while he was with the Malaria training corps at the Gulf of Trieste, and was