Azerbaijan is a country in the Caucasus region of Eurasia. Located at the crossroads of Eastern Europe and Western Asia, it is bounded by the Caspian Sea to the east, Russia to the north, Georgia to the northwest, Armenia to the west, and Iran to the south. The exclave of Nakhichevan is bounded by Armenia to the north and east, Iran to the south and west, while having a short borderline with Turkey to the northwest. The majority-Armenian populated Nagorno-Karabakh region in the southwest of Azerbaijan proper declared itself independent from Azerbaijan in 1991, but it is not recognized by any nation and considered a legal part of Azerbaijan.
The region was part of a succession of empires for much of its history, including Russia. It became the first modern Muslim republic in the immediate aftermath of World War I. It existed independently for a few years before it was reconquered by the Soviet Union. It regained its independence in 1991.
In the home timeline, the ongoing conflict between Armenia and Azerbaijan for control of the Nagorno-Karabakh was ended in the 21st century when an extremist group released a tailored form of Ebola into the region. All human life in Nagorno-Karabakh was wiped out, as well as in adjacent areas of Azerbaijan, making them permanently uninhabitable and strictly quarantined.
The identity of the perpetrators remained unknown, as they were assumed to have themselves perished by the disease which they unleashed. Armenians and Azeris blamed each other in the years that followed.
Azerbaijan and its neighbor Armenia had a centuries-old feud. Anastas Mouradian, an Armenian pilot in the Soviet Air Force, felt quite alienated and out of place in the Russian-dominated environment of the USSR, though he made a big effort not to show it. In the later part of the war he was assigned an Azeri co-pilot. Though the Christian Armenians and Muslim Azeris were hereditary enemies, Mouradian still felt that the two of them - having a shared geographical and historical background - had more in common than either one had with the Russians around them.