In the 12th century, Pope Adrian IV made Henry II of England overlord of the island. Centuries of British dominion in Ireland gave rise to unrest which finally erupted into violence with the Easter Rising of 1916, when Ireland proclaimed independence. Although the rising was crushed and many of its leaders executed, the campaign for independence carried on through a bloody Anglo-Irish War of 1919-1921. In 1922, 26 counties of Ireland gained independence from London following negotiations which led to the other six counties, part of the province of Ulster, remaining in the United Kingdom. Relations between Ireland and the UK remained strained for many years after Ireland’s independence, while Northern Ireland saw decades of violent conflict between those campaigning for a united Ireland and those wishing to stay in the United Kingdom. In an unprecedented and concerted effort to resolve the situation, the Irish and UK governments worked closely together in negotiations which led to the Good Friday Agreement on the future of Northern Ireland in 1998. The peace settlement for Northern Ireland is gradually being implemented despite some difficulties. Since joining the European Community (now the EU) in 1973, the small economy of Ireland has been transformed from a largely agricultural society into a modern, technologically-advanced one. Ireland's economy grew rapidly in the 1990s fueled by foreign investment. But in recent years its economic growth became increasingly unbalanced with easy credit supply accommodating an unsustainable rise in property prices, making it significantly vulnerable to the global economic and financial crisis in 2008.