The Military Service (No. 2) Act, 1918 attempts to extend conscription to Ireland. April 9, 1918.

And would, accordingly, prove to be a big mistake.

The Irish had volunteered in large numbers to serve in the British Army during World War One, which of course was their army as they were part of the United Kingdom.  In spite of that, this did not mean by any means that all was well with the relations between Ireland and London.  It had never been, although that relationship had improved greatly over the last couple of decades.

The improvement of that relationship lead to a movement towards home rule that would have almost certainly caused Ireland to be self governing on domestic maters, while still part of the United Kingdom, by 1915 but for the arrival of World War One.  At that point all discussion on this topic was surrendered for the duration of the war.  Parliament had been cognizant, however, that Ireland's situation was fluid and it had not extended conscription to Ireland.  The strained relationship had, of course, lead to the Easter Rebellion of 1916, but that uprising had not been supported by the majority of the Irish and indeed was unpopular at the time.

Faced with the crisis of the German Spring Offensive and a severe immediate military crisis, Parliament finally acted to extend conscription to Ireland on this date.  

That would prove to be a grave error, just as it would prove to be in Canada.