Hederstedt was appointed battalion commander of the Swedish UN Battalion of the United Nations Interim Force in Lebanon (UNIFIL) in Lebanon in 1988. In Lebanon, Hederstedt conducted many negotiations on various levels with several of the factions (e.g., PLO, PFLP, Hezbollah, Black September, Amal, etc. and Israeli supported Christian guerrilla parties). He was commanding officer of the Life Guards Brigade (MekIB 1) at Svea Life Guards (I 1) in Kungsängen from 1988 to 1993. Between 1989 and 1992 Hederstedt was also the Course Director for UN Nordic Staff officers courses dealing with guerilla warfare. He also conducted fact-finding trips to troublespots, including Cyprus, Kuwait, Iraq, Iran, and the Middle East (Israel, Gaza, and Lebanon). Hederstedt was commanding officer of the Western Army Division in Skövde from 1993 to 1996. Hederstedt was promoted to major general in 1996 and was appointed International Operations Commander at the Swedish Armed Forces Headquarters.