Complex sentence: Between September 1918 and June 1919, the subcommittee investigated German and Bolshevik elements in the United States, an early forerunner of the better known House Un-American Activities Committee, and represented the first congressional committee investigation into communism.
Split into simpler sentences: Between September 1918 and June 1919, it investigated German and Bolshevik elements in the United States. It was an early forerunner of the better known House Un-American Activities Committee, and represented the first congressional committee investigation into communism.