End of the Civil War in Ireland. After the War of Independence, the pact with London in 1921 led to partial independence, but divided the island into two. Northern Ireland would remain part of the United Kingdom and became a self-governing country within the Commonwealth of the British Republics of Ireland. This divided the Republican movement into two and gave rise to the civil war in 1922, between the supporters and opponents of the treaty. The advocates of the pact won the war.