were a Gaelic Irish tribe, generally accepted by contemporary
scholarship as being a branch of the Déisi Muman, that became a
powerful group in Ireland during the 10th century. Their
genealogies claimed descent from Cormac Cas, who is said to have
lived in the 3rd century AD. Their known ancestors are the
subject of The Expulsion of the Déisi tale and one branch
of their blood-line went on to rule the petty kingdom of Dyfed
in Wales during the 4th century; probably in alliance with Roman
emperor, Magnus Maximus.
Brian Bóruma is
perhaps the best known king from the dynasty and was responsible
to a significant degree for carving out their fortunes. The
family had built a powerbase on the banks of the River Shannon
and Brian's brother Mahon became their first King of Munster,
taking the throne from the rival Eóganachta. This influence was
greatly extended under Brian who became High King of Ireland,
following a series of conflicts with Norse and other Irish
tribes, before dying famously at the Battle of Clontarf in 1014.
Following this the Dál gCais provided three more High Kings of
Ireland; Donagh O'Brien, Turlough O'Brien and Murtagh O'Brien.
12th–16th centuries, the Dál gCais contented themselves with
being reduced to the Kingdom of Thomond. They attempted to claim
the Kingdom of Desmond for a time, but ultimately the MacCarthys
held it. The Kennedys also held the Kingdom of Ormond for a
time. Some of the better known septs included O'Brien, Moloney,
MacNamara, O'Grady, Kennedy, MacMahon, McInerney, and Clancy.
During the 13th century Richard Strongbow's relatives the Norman
de Clares attempted to take Thomond, but the Dál gCais held
It wasn't until
the 16th century, unable to be defeated militarily, they agreed
to surrender and grant their kingdom to Henry VIII Tudor,
joining the nobility of the Kingdom of Ireland. Their realm was
renamed County Clare, though they remained influential. In later
times, remarkable figures include writer Standish James O'Grady,
who is called "Father of the Celtic Revival" and William Smith
O'Brien who played a leading part in the Young Irelander
Rebellion of 1848. In diaspora, prominent figures have included
Marshal Patrice de Mac-Mahon, President of France, as well as
John F. Kennedy and Ronald Reagan.