Complex sentence: While never one of Khrushchev's protëgës, Kosygin quickly moved up the party ladder and was promoted to head of the State Planning Committee and became Khrushchev's First Deputy Premier in 1960, and regained his old seat in the Politburo.
Split into simpler sentences: While never one of Khrushchev's protëgës, Kosygin quickly moved up the party ladder. He was promoted to head of the State Planning Committee and became Khrushchev's First Deputy Premier in 1960, and regained his old seat in the Politburo.