Complex sentence: The Armagh rail disaster happened on 12 June 1889 near Armagh, Irelandand was when a crowded Sunday school excursion train had to negotiate a steep incline, but the steam locomotive was unable to complete the climb and the train stalled.
Split into simpler sentences: The Armagh rail disaster happened on 12 June 1889 near Armagh, Ireland. A crowded Sunday school excursion train had to negotiate a steep incline, but the steam locomotive was unable to complete the climb and the train stalled.