Complex sentence: Child founded the Progressive Republican League in Massachusetts, a forerunner of the Progressive Party, and during World War I, he worked first as a correspondent in Europe and Russia, then for the U.S. Treasury, writing propaganda.
Split into simpler sentences: Child founded the Progressive Republican League in Massachusetts, a forerunner of the Progressive Party. During World War I, he worked first as a correspondent in Europe and Russia, then for the U.S. Treasury, writing propaganda.