Had Philip of Spain sent his son as King to Ireland, her fate had been settled then instead of remaining three centuries later to still confront European statesmanship with an unsolved problem.
In many letters addressed by the Irish leaders to Philip II and Philip III we find the constantly recurring note of warning that to leave England in possession of Ireland meant the downfall of Spain.

The Irish princes knew that in fighting England they were in truth fighting the battle of European civilization.
Writing to Philip II from Lifford, on May 16th, 1596, O'Neill and O'Donnell drew the King's attention to the cause of Ireland as the cause of Europe, and in the name of Ireland offered the crown to a Spanish prince.

"But inasmuch as we have felt to our great and indescribably harm the evil doings and crimes of those whom the Queen of England is in the habit of sending amongst us, we beg and beseech Your Majesty to send someone well known to you and perfectly fit to be the King of this island, for his own welfare, ours, and that of the Christian State (Christendom)." They asked for a prince "who will not be unwilling to rule over and live amongst us and to direct and guide our nation, well and wisely." They pointed out how "he will obtain much advantage and glory by so doing," and finally they begged "would that Your Majesty would appoint the Archduke of Austria, now Governor of Flanders, a famous man and worthy of all praise, than whom none would be more acceptable." (The original is in Latin and in the archives of Simancas.) No more statesmanlike appeal was ever made from Ireland; and had the Archduke of Austria assumed the crown of Ireland in 1596, "now or never" would indeed have become "now and forever." Had Philip II carried out his often repeated promises of sending aid to that country the fate of his own kingdom must have been a very different one.
"I wish it were possible for me, by word of mouth, to show the importance of this undertaking and the great service that would be rendered thereby to God and His Church, and _the great advantage it would be to the service of Your Majesty and the peace of Your States to attack the enemy here_." So wrote in 1600 to Philip II, the Archbishop of Dublin, already quoted, Mattheo de Oviedo.
This prelate had been specially sent to Ireland "to see and understand the state of the country misrepresented by English emissaries at foreign courts." The wrath of Elizabeth against O'Neill was largely due to his keeping in touch with the continent, whereby the lies of her agents abroad were turned to her own ridicule.

To Essex, her Viceroy, she wrote: "Tyrone hath blazed in foreign parts the defeat of regiments, the death of captains, and loss of men of quality in every quarter." O'Neill not only for years beat her generals in the field, her beat herself and her councillors at their own game.

To Essex, in an ecstacy of rage at the loss of the last great army sent, she wrote (September 17th, 1599): "To trust this traitor upon oath is to trust the devil upon his religion.