Complex sentence: The out-of-uniform soldiers were killed by the Provisional Irish Republican Army (IRA), after they drove into the funeral procession of an IRA member killed three days beforehand when loyalist Michael Stone had attacked an IRA funeral and killed three people.
Split into simpler sentences: The out-of-uniform soldiers were killed by the Provisional Irish Republican Army (IRA), after they drove into the funeral procession of an IRA member. Three days beforehand, loyalist Michael Stone had attacked an IRA funeral and killed three people.