Nygren steadily ascended the ranks, reaching the positions of major, Vice Chief of the Military Office of the Ministry of Land Defence, and lieutenant colonel at the General Staff.

His noteworthy roles included leading the Royal Swedish Army Staff College and serving as the Chief of the Military Office of the Ministry of Land Defence.

Nygren also contributed to various international committees as a military expert and chaired a pension insurance company.

During World War II, he was called back into service as the commander of the newly formed 2nd Army Corps, holding leadership positions in Upper Norrland and West Sweden, showcasing his contributions to the military and international committees.

[1] He was Vice Chief of the Military Office of the Ministry of Land Defence in 1915 and was lieutenant colonel at the General Staff in 1915.

He was appointed Chief of the Military Office of the Ministry of Land Defence in 1919 conducted a study trip to the Italian Front in 1922.