An expedition of Cambro-Norman knights with an army of about six hundred lands at Bannow Strand in present-day County Wexford on May 1, 1169.

It is led by Richard de Clare, called Strongbow due to his prowess as an archer.

The invasion, which coincides with a period of renewed Norman expansion, is at the invitation of Dermot Mac Murrough, the king of Leinster.

In 1166, Mac Murrough had fled to Anjou, France, following a war involving Tighearnán Ua Ruairc, of Breifne, and sought the assistance of the Angevin king, Henry II, in recapturing his kingdom.

In 1171, Henry arrives in Ireland in order to review the general progress of the expedition.

He wants to re-exert royal authority over the invasion, which is expanding beyond his control.

Henry successfully re-imposes his authority over Strongbow and the Cambro-Norman warlords and persuades many of the Irish kings to accept him as their overlord, an arrangement confirmed in the 1175 Treaty of Windsor.

The invasion is legitimized by the provisions of the Papal Bull Laudabiliter, issued by Adrian IV in 1155.

The bull had encouraged Henry to take control in Ireland in order to oversee the financial and administrative reorganization of the Irish Church and its integration into the Roman Church system.

Some restructuring had already begun at the ecclesiastical level following the Synod of Kells in 1152.

There has been significant controversy regarding the authenticity of Laudabiliter, and there is no general agreement as to whether the bull was genuine or a forgery.

In 1172, the new pope, Alexander III, further encourages Henry to advance the integration of the Irish Church with Rome.

Henry is authorized to impose a tithe of one penny per hearth as an annual contribution.

This church levy, called Peter's Pence, is extant in Ireland as a voluntary donation.

In turn, Henry accepts the title of Lord of Ireland, which Henry confers on his younger son, John Lackland, in 1185.

When Henry's successor dies unexpectedly in 1199, John inherits the crown of England and retains the Lordship of Ireland.