Nevanlinna began his studies at the University of Helsinki in 1913, and received his Master of Philosophy in mathematics in 1917. Lindelöf taught at the university and Nevanlinna was further influenced by him. During his time at the University of Helsinki, World War I was underway and Nevanlinna wanted to join the 27th Jäger Battalion, but his parents convinced him to continue with his studies. He did however join the White Guard in the Finnish Civil War, but did not see active military action. In 1919, Nevanlinna presented his thesis, entitled "Über beschränkte Funktionen die in gegebenen Punkten vorgeschriebene Werte annehmen" ("On limited functions prescribed values at given points"), to Lindelöf, his doctoral advisor. The thesis, which was on complex analysis, was of high quality and Nevanlinna was awarded his Doctor of Philosophy on 2 June 1919.