Complex sentence: In the Irish Civil War of 1922-1923, he took the pro-treaty side and was put in charge of the Intelligence service of the new state, the Crime Investigation Department or CID.
Split into simpler sentences: In the Irish Civil War of 1922-1923, he took the pro-treaty side and was made Director of Intelligence. He was put in charge of the Intelligence service of the new state, the Criminal Investigation Department or CID.