Complex sentence: His sire, Prince Rose, had been standing at the Haras de Cheffreville stud farm in France and was mated to the mare Cosquilla but when World War II broke out, the pregnant mare was shipped to Ireland where she gave birth to Princequillo.
Split into simpler sentences: His sire, Prince Rose, stood at the Haras de Cheffreville stud farm in France and was mated to the mare Cosquilla. When World War II broke out, the pregnant mare was shipped to Ireland, where she gave birth to Princequillo.