According to legend, St. Patrick arrived in 432 CE, bringing Christianity which eventually lead to the collapse of the druid tradition. Ireland's status as a centre of high-learning during the Early Middle Ages was interrupted in the 9th century by 200 years of Viking invasions. Eventually the Vikings settled down (in Ireland).
In the 1840s, the Great Famine killed at least one million Irish people, and forced another million to emigrate. The Irish-Anglo war of 1922 lead to the formation of the Irish Free State. A civil war followed, and the Irish Republic was declared in 1949.