In prehistoric times Ireland underwent a
number of invasions from Europe, the most
important of which was that of the Gaels in
the 3rd century BC. Gaelic Ireland was
divided into kingdoms, nominally subject to
an Ardri or High King; the chiefs were
elected under the tribal or Brehon law, and
were usually at war with one another.
Christianity was introduced by St Patrick
about 432, and during the 5th and 6th
centuries Ireland became the home of a
civilization which sent out missionaries to
Britain and Europe. From about 800 the Danes
began to raid Ireland, and later founded
Dublin and other coastal towns, until they
were defeated by Brian Boru (king from 976)
at Clontarf 1014. Anglo-Norman adventurers
invaded Ireland 1167, but by the end of the
medieval period English rule was still
confined to the Pale, the territory around
Dublin. The Tudors adopted a policy of
conquest, confiscation of Irish land, and
plantation by English settlers, and further
imposed the Reformation and English law on
Ireland. The most important of the
plantations was that of Ulster, carried out
under James I 1610. In 1641 the Irish took
advantage of the developing struggle in
England between king and parliament to begin
a revolt which was crushed by Oliver Cromwell
1649, the estates of all `rebels' being
confiscated. Another revolt 1689-91 was also
defeated, and the Roman Catholic majority
held down by penal laws. In 1739-41 a famine
killed one-third of the population of 1.5
million. During another famine 1845-46, 1.5
million people emigrated, mostly to the USA.
The Easter Rising took place in Apr 1916,
when nationalists seized the Dublin general
post office and proclaimed a republic. After
a week of fighting, the revolt was suppressed
by the British army and most of the leaders
executed. From 1918-21 there was guerrilla
warfare against the British army, especially
by the Irish Republican Army (IRA), formed by
Michael Collins 1919. This led to a split in
the rebel forces, but in 1921 the Anglo-Irish
Treaty resulted in partition and the creation
of the Irish Free State in S Ireland. For
history since that date, see Ireland,
Republic of; Ireland, Northern.