Complex sentence: This was a paramilitary unit composed of ex-soldiers from Britain which specialized in counter-insurgency and recruited thousands of British ex-soldiers into the RIC, who became known as "Black and Tans".
Split into simpler sentences: This was a paramilitary unit composed of ex-soldiers from Britain which specialized in counter-insurgency. It also recruited thousands of British ex-soldiers into the RIC, who became known as "Black and Tans".