Complex sentence: It was initially deployed at the request of the unionist government of Northern Ireland to support the Royal Ulster Constabulary (RUC), but its role soon became one of asserting the authority of the government of the United Kingdom in Northern Ireland.
Split into simpler sentences: It was initially deployed at the request of the unionist government of Northern Ireland to support the Royal Ulster Constabulary (RUC). Its role was to assert the authority of the Government of the United Kingdom in Northern Ireland.