Sinn Fein

Sinn Fein, the political organization, had been formed at the beginning of the 20th century. The words are Gaelic and they literally mean, 'ourselves alone.' They mean that we can go and achieve our own freedom, we don't need the help of anyone else do it, but that we have to be a free-standing nation among the nations of the world, and therefore the only answer is Irish unity.

Now, some of them believed in some sort of relationship with Britain, but Irish unity was the be-all and end-all of their policy. Sinn Fein was a constitutional party, and in fact, at the British general elections in 1918, Sinn Fein won the majority of seats throughout the island of Ireland, and it was that which gives them the animus to conduct a violent campaign against the British in the War of Liberation. And it was that war which persuaded the British to withdraw from Ireland, but to withdraw through a partition settlement.

(Source:  http://www.pbs.org/wgbh/pages/frontline/shows/ira/conflict/gasf.html)