Complex sentence: He became the Prime Minister of Latvian SSR and served in this position from 1940 to 1959, largely in a figurehead role, as most of the actual decisions were made by Central Committee of the Communist Party.
Split into simpler sentences: He became the Prime Minister of the Latvian SSR and served in this position from 1940 to 1959. He was regarded mostly as a figurehead, as most of the actual decisions were made by Central Committee of the Communist Party.