The other thread has better material than I could provide, but I’ll throw this in anyway since I already looked it up:
After consulting a book I have with a very thin history of the area, and a quick Google check, I don’t have much concrete info. But here goes.
Between July 1960 and November 1967, the former Belgian colony of the Congo (Zaire) was involved in almost continuous civil war. Brought about by continuous tribal and political tensions, attempted sessesions and rebellions, outside inference, and the vacuum left by the departed Belgians.
On May 30, 1967, the predominatly Ibo Eastern Region of Nigeria decalred its independence, creating the Republic of Biafra. It survived through three years of fighting until it was forced to surrender to the Federal forces of General Yabaku Gowon in January 1970 and reunite with Nigeria.
White, mostly European and some South African, mercenaries were involved in both wars. They fought on the side of Moise Tshumbo in the Congo. They also fought for Lieutenant-Colonel Chukwuemeka Ojukwu’s sessesionist forces in Biafra.
I agree that Roland and Van Owen are fictional, and Zevon that combined the wars in the song for his own purposes. It would make sense that mercenaries would bounce from war to war as needed considering the nature of the job and the irregularity of employment. My book makes no mention of CIA involvement in either conflict, but I don’t doubt it and the other thread covers their participation, besides it makes for a better song.
Zevon may have drawn his inspiration for the names from actual mercenaries. A Rolf Steiner fought in both wars I mentioned. From what little I could gleen from Google, most of it was in German, he was still alive as of 2001.
A Count Carl Gustav von Rosen flew Swedish-built Minicon light aircraft against the Federal forces of Nigeria in 1969 while in the employ of Biafra. According to Google, he died in 1977.