Complex sentence: By far the most dangerous threat to the Tudor line during Elizabeth's reign was the Spanish Armada of 1588, launched by Elizabeth's old suitor Philip II of Spain and commanded by Alonso de Guzmán El Bueno, the seventh Duke of Medina Sidonia.
Split into simpler sentences: By far the most dangerous threat to the Tudor line during Elizabeth's reign was the Spanish Armada of 1588. Launched by Elizabeth's old suitor Philip II of Spain, this was commanded by Alonso de Guzmán El Bueno, the seventh Duke of Medina Sidonia.