Complex sentence: In 1990, Sargsyan became the head of the Defence Committee of the Armenian parliament and soon after Armenia's independence from the Soviet Union in September 1991, he was appointed Defence Minister of Armenia by President Levon Ter-Petrosyan.
Split into simpler sentences: In 1990, Sargsyan became the head of the Defence Committee of the Armenian parliament. After Armenia's declaration of independence in September 1991, he was appointed Defence Minister of Armenia by President Levon Ter-Petrosyan.