Complex sentence: In the early years of the Troubles, the IRA in Belfast expanded rapidly; in August 1969, the Belfast Brigade had just 50 active members-by the end of 1971, it had 1,200 members, giving it a large but loosely controlled structure.
Split into simpler sentences: In the early years of the Troubles, the IRA in Belfast expanded rapidly. By the end of 1971, it had 1,200 members, giving it a large but loosely controlled structure.