Complex sentence: Following collapse of the Soviet Union, Ukraine's was formed as an independent state in 1991, most of the peninsula was reorganized as the Autonomous Republic of Crimea, while the city of Sevastopol retained special status within Ukraine.
Split into simpler sentences: Following collapse of the Soviet Union, Ukraine was formed as an independent state in 1991. Most of the peninsula was reorganized as the Autonomous Republic of Crimea, while the city of Sevastopol retained its special status within Ukraine.