Ireland was inhabited by Celts from about the 6th century BC. English invasions began in the 12th century under Henry II, although the whole of the island was not conquered until the time of the Tudors. Revolts against English rule led to English and Scottish families being settled on confiscated land; in parts of Ulster the descendants of Protestant settlers form a majority. After an unsuccessful rebellion in 1798, union of Britain and Ireland followed in 1801. Increased prosperity was experienced in Protestant Ulster, but not in the rest of the island, and after the failure of of the potato crop in the 1840s thousands died in a famine, and thousands more emigrated. In 1922 Ireland was partitioned by the Anglo-Irish Treaty.