Complex sentence: After the Russian Revolution of 1905 he went abroad to study in Vienna and became one of the editors of Leon Trotsky's original "Pravda" in 1908-1912.
Split into simpler sentences: After the Russian Revolution of 1905 he went abroad to study in Vienna. While in Vienna, he became one of the editors of Leon Trotsky's original "Pravda" in 1908-1912.