 During the twentieth century, the Commonwealth of Nations evolved from the British Empire. Prior to 1926, the British Crown reigned over the British Empire collectively; the Dominions and Crown colonies were subordinate to the United Kingdom. The Balfour Declaration of 1926 gave complete self-government to the Dominions, effectively creating a system whereby a single monarch operated independently in each separate Dominion. The concept was solidified by the Statute of Westminster 1931, which has been likened to "a treaty among the Commonwealth countries".
