Complex sentence: He became the captain of Polar ship "Zarya" during the last part of Baron Eduard Toll's expedition on behalf of the the Russian Academy of Sciences, the Russian Polar Expedition (1900--1903).
Split into simpler sentences: He became the captain of Polar ship "Zarya" during the last part of Baron Eduard Toll's expedition on behalf of the the Russian Academy of Sciences. This expedition was known as the Russian Polar Expedition (1900--1903).