Complex sentence: He was dismayed by what he saw as the revisionism of Nikita Khrushchev following the death of Joseph Stalin, and he apparently broke with the party when CPI, during an underground period, it supported Khrushchev's criticisms of Stalin.
Split into simpler sentences: He was dismayed by what he saw as the revisionism of Nikita Khrushchev following the death of Joseph Stalin. He apparently broke with the party when CPI, during an underground period, supported Khrushchev's criticisms of Stalin.