Attempts to either conquer or assimilate the Irish lordships into the Kingdom of Ireland provided the initial impetus for a series of Irish military campaigns between 1534 and 1603. This period was marked by a Crown policy of plantation, involving the arrival of thousands of English and Scottish Protestant settlers, and the consequent displacement of the pre-plantation Catholic landholders. As the military and political defeat of Gaelic Ireland became more pronounced in the early seventeenth century, sectarian conflict became a recurrent theme in Irish history.