There is no archaeological confirmation of the great Celtic invasion of Ireland. These could have been invasions by small groups or long-term peaceful influxes and cultural influences of the Celts, which led to the assimilation of the local population and the creation of a Celticized society in the sense of sharing a common Celtic culture and language. They divided Ireland into four provinces: Leinster, Munster, Ulster and Connacht. Before their arrival, the basic units of Irish society were the Tuatha, or petty kingdoms. The entire territory was ruled by a monarch called the Great King.
