In 1936, Azerbaijan became a republic in the Soviet Union. They made this change because of their involvement in WWII. They were also under Soviet influence to make this change.
The ethnic strife starts to escalate in 1990. Armenians and Azeris are now begging to fight. The speculation about the two Azerbaijans becoming unified under Soviet control also rises tension.
The USSR ends after the cold war and becomes independent. This causes ethnic strifes to return. The fighting in Nagorno-Karabakh turns into a full scale war. Later in the year on December 26, 1991, the dissolution of Soviet Union occurs.
Iranian government regained control over Iranian Azerbaijan. After this the Soviet Union the withdrawn. During this the U.S did everything they could to stop it.
Azerbaijan later returns to a policy of Russification. During this time they had a new anti- Islamic drive. They then ordered to merge the people of the USSR into a new monolithic Soviet nation.