Complex sentence: Suontausta had a significant background role as a legal adviser to President Paasikivi specially dealing with the Stalin's proposal for the Finno-Soviet Treaty in the late winter of 1948.
Split into simpler sentences: Suontausta had a significant background role as a legal adviser to President Paasikivi. He was especially important in dealing with Stalin's proposal for the Finno-Soviet Treaty in the late winter of 1948.