Complex sentence: Other horsed regiments in the British Army, during the war, were the regular cavalry regiments and the three regiments belonging to the special reserve: the North Irish Horse, the South Irish Horse and the King Edward's Horse.
Split into simpler sentences: Other horsed regiments in the British Army, during the war, were the regular cavalry regiments and the three regiments belonging to the special reserve. The North Irish Horse, the South Irish Horse and the King Edward's Horse.