But not everyone agrees.

People in six northern counties - largely Protestants - want their province of Ulster (once a British plantation) to be part of the United Kingdom. People in twenty-six southern counties - largely Catholics - want an independent Ireland, free of United Kingdom rule.

A treaty with Britain, signed on 6 December 1921, is now before the Irish Parliament. If passed, Ireland will split in two. Twenty-six counties in the south would be an independent country; six counties in the north would be part of the United Kingdom.

After heated debates, the Anglo-Irish Treaty passes by a narrow vote.

Some people, in the newly independent south, believe the partition of their country is the best that Ireland can achieve - for now. Others bitterly oppose splitting the country in two. Insurgents on both sides have built-up arms. Sectarian violence is about to erupt, causing an Irish civil war.

Why would the Irish people, who had endured such anguish for centuries, now kill each other?