Complex sentence: During the January Uprising in 1863 heavy city fights occurred, but were brutally pacified by Mikhail Muravyov, nicknamed "The Hanger" by the population because of the number of executions he organized.
Split into simpler sentences: During the January Uprising in 1863 heavy city fights occurred, but were brutally pacified by Mikhail Muravyov. Muravyov was nick-named "The Hanger" by the population because of the number of executions he organized.