Complex sentence: He later left the republic for the other parts of the Soviet Union and was reportedly working in the construction in Russia, either in Moscow or in Tyumen Oblast, when the First Chechen War began in December 1994.
Split into simpler sentences: He later left the republic for work in the other parts of the Soviet Union. He was working in the construction either in Moscow or in Tyumen Oblast when the First Chechen War began in December 1994.