Sagrén served at the Life Grenadier Regiment (I 4) and the Army Ranger School from 1958 to 1967 and was completed the higher course of the Swedish Armed Forces Staff College from 1967 to 1969. He then served at the Army Staff from 1969 to 1973 and the Eastern Military District (Milo Ö) from 1973 to 1976. He served in the Defence Staff from 1976 to 1982 and was commanding officer of the Västernorrland Regiment (I 21) and Sollefteå Army Garrison from 1982 to 1983. Sagrén was commanding officer of the Västernorrland Regiment and was Defence District Commander of the Västernorrland Defense District (Fo 23) from 1983 to 1984. On 1 April 1984, he became director  and head of the Planning and Budget Secretariat (PBS) at the Ministry of Defence in Stockholm. He was promoted to major general in 1985 and on 1 October 1986, he assumed the position of chief of staff of the Upper Norrland Military District (Milo ÖN). On 1 October 1988, Sagrén assumed the position of military commander of the Upper Norrland Military District, succeeding lieutenant general Lars-Erik Englund. On 1 April 1990, Sagrén suceeded lieutenant general Erik G. Bengtsson as Chief of the Army. He held the post until 30 June 1994 and the post of Chief of Army Command from 1 July 1994 to 1996.