Complex sentence: He became an official in the Communist Party of the Soviet Union, becoming the First Secretary of the Uzbek Communist Party in 1989 after his predecessor Rafiq Nishonov failed to quell inter-ethnic clashes and instability in the Fergana Region.
Split into simpler sentences: He became an official in the Communist Party of the Soviet Union, becoming the party's First Secretary in Uzbekistan in 1989. Karimov's election to the Uzbek Communist Party resulted after his predecessor Rafiq Nishonov failed to quell inter-ethnic clashes and instability in the Fergana Region.