Jokipii attended University of Helsinki from 1952 to 1959, and began publishing almost immediately (1954).
He was a thorough investigator and a prolific author Among his works were studies of the local history of Jyväskylä and the university and historical province of Satakunta. He received his doctorate in Philosophy in 1957.
He was Dean of the History-Linguistics department from 1960 to 1966.
Although some of his early works had been noted, Jokipii sprung on the world scene with his 900-page study of the Finnish Steamship battalion in World World War World War II This study established a new level of detail in World World War II military history. Jokipii"s massive work The Continuation War: An Investigation of German-Finnish Military Collaboration 1940-1941 firmly established him as a world scholar and moved the debate about German Finnish relations during World World War II to a new level
Jokipii died in Jyväskylä.