 He became a second lieutenant in Hälsinge Regiment (I 14) in 1892 and studied at the Royal Swedish Army Staff College from 1896 to 1898 and was a cadet at the General Staff from 1898 to 1901.Nygren became a lieutenant at the General Staff in 1902 and was promoted to captain in 1904.He was adjutant to the head of the Ministry of Land Defence from 1907 to 1910 and was transferred to Hälsinge Regiment (I 14) in 1909.