Complex sentence: Makarov proposed the idea, oversaw the construction the World's first icebreaker, the "Yermak", and commanded her on two Arctic expeditions in 1899 and 1901.
Split into simpler sentences: Makarov proposed the World's first icebreaker, the "Yermak". He oversaw her construction and commanded her on two Arctic expeditions in 1899 and 1901.