Complex sentence: When Trotsky was nine, his father sent him to Odessa to be educated and he was enrolled in an historically German school, which became Russified during his years in Odessa, consequent to the Imperial government's policy of Russification.
Split into simpler sentences: When Trotsky was nine, his father sent him to Odessa to be educated. He was enrolled in an historically German school, which became Russified during his years in Odessa, consequent to the Imperial government's policy of Russification.