Overview
The state known today as Ireland is the successor-state to the Irish Free State which was established in 1922. The Free State was governed, until at least 1936, under a form of constitutional monarchy; the King had a number of important duties, including exercising the executive authority of the state, appointing the cabinet and promulgating the law. However, in 1936, the Free State constitution was amended to remove all of the functions performed by the King except one, that of representing the state abroad. The outcome of the constitutional change made in 1936 was that, while he was mentioned nowhere explicitly in the constitution, Irish ministers continued to sign international treaties in the King's name, and the King continued to accredit Irish ambassadors, and receive the letters of credence of foreign diplomats.
In 1937 a new constitution was adopted which renamed the state to simply 'Ireland' and entrenched the monarch's diminished role, transferring many of the functions performed by the King until 1936 to a new office of President of Ireland, who was declared to "take precedence over all other persons in the State". However, the 1937 constitution did not explicitly declare that the state was a republic, nor that the president was head of state, and it allowed the King to retain his role in foreign affairs. The state's ambiguous status ended in 1949, when the Republic of Ireland Act stripped the King of his role in foreign affairs and declared that the state was a republic.
The status of the Head of the Irish State from 1936 to 1949 was largely a matter of symbolism and had little practical significance. This was because the roles of both the King and the President of Ireland were merely ceremonial, being exercisable only "on the advice" of the Government (Cabinet). However, one practical implication of explicitly declaring the state to be a republic in 1949 was that it automatically terminated the state's membership of the then British Commonwealth, in accordance with the rules in operation at the time.
Read more about this topic: Irish Head Of State From 1936 To 1949