WI Henry II invades Ireland earlier and makes his brother king?

From the Wikipedia page about William FitzEmpress, brother of Henry II of England:

"In September 1155, King Henry held a council at Winchester where he enthusiastically considered invading Ireland and giving it to William, making him king. The plans were abandoned when their mother, Empress Matilda, objected: she did not consider Ireland worth conquering."

So, WI Matilda had not objected to it? How would Henry fare in an earlier invasion of Ireland?

What would be the possible motive/s behind this invasion of Ireland and the installation of William as its king had Empress Matilda allowed it.

ramones1986 said:

What would be the possible motive/s behind this invasion of Ireland and the installation of William as its king had Empress Matilda allowed it.

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England would have a close vassal, I think many Englishmen at the time were worried that some one like the French or the Scots would conquer it and have it as a base for a three way invasion.
If England controlled the Island through a blood relative it would tale away a bit of the strain.

Also at this point in time, William is 19, a good age for a king and as he is still single, he is in a key position to get any bride of his choice:
- Isabel de Warenne, Countess of Surrey
And start a Plantagenet line in Ireland.

ramones1986 said:

What would be the possible motive/s behind this invasion of Ireland and the installation of William as its king had Empress Matilda allowed it.

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Well, he certainly was interested in doing it. In that same year - 1155 - the Pope Adrian IV issued a bull grating Henry the right to invade Ireland on the behalf of the Church. About the reason for giving it to William, maybe because he was extremely loyal to him (contrary to his brother Geoffrey)? He did after all make him very rich by granting him a lot of land and titles.

Jonathan said:

England would have a close vassal, I think many Englishmen at the time were worried that some one like the French or the Scots would conquer it and have it as a base for a three way invasion.
If England controlled the Island through a blood relative it would tale away a bit of the strain.

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I haven't heard anything like that and the Scots were completely incapable of conquering Ireland; they had enough troubles absorbing the old Kingdom of the Isles at this point still less Ireland. The French did not even control northern France.

Jonathan said:

Also at this point in time, William is 19, a good age for a king and as he is still single, he is in a key position to get any bride of his choice:
- Isabel de Warenne, Countess of Surrey
And start a Plantagenet line in Ireland.

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How about choosing a bride from either native Irish clans or Hiberno-Norman nobles?

Gonzaga said:

Well, he certainly was interested in doing it. In that same year - 1155 - the Pope Adrian IV issued a bull grating Henry the right to invade Ireland on the behalf of the Church.

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So King Henry II wanted to invade Ireland in order to bring the Emerald Isle closer to Roman Catholic Church? This is really interesting!

ramones1986 said:

So King Henry II wanted to invade Ireland in order to bring the Emerald Isle closer to Roman Catholic Church? This is really interesting!

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Yes, very ironic.

Here the text of the papal bull of 1155: http://www.libraryireland.com/HullHistory/Appendix1a.php

This is the part where it allows Henry to conquer Ireland:

"You have signified to us, our well-beloved son in Christ, that you propose to enter the island of Ireland in order to subdue the people and make them obedient to laws, and to root out from among them the weeds of sin; and that you are willing to yield and pay yearly from every house the pension of one penny to St Peter, and to keep and preserve the rights of the churches in that land whole and inviolate.

We, therefore, regarding your pious and laudable design with due favour, and graciously assenting to your petition, do hereby declare our will and pleasure, that, for the purpose of enlarging the borders of the Church, setting bounds to the progress of wickedness, reforming evil manners, planting virtue, and increasing the Christian religion, you do enter and take possession of that island, and execute therein whatsoever shall be for God's honour and the welfare of the same."