He knew that if Ireland said nothing and did nothing at the crisis, things would be said of Ireland which would rapidly engender rising passion; and with the growth of that passion all possibility, not of bargaining but of controlling the situation between the two countries would be gone.

In plain language, if he had not acted at once, his only chance for action would have been in heading an Ireland hostile to England.

In this war, with the issue defined as it was from the outset, he could only have done this by denying all that he believed.

But apart from his judgment of the merits, there was his purpose of unity to be served.

Ulster was the difficulty; all other obstacles were disposed of.
How could he hope for an Ulster united to Ireland, if Ulster were divided from Ireland on the war?
Everything depended on an instant and almost desperate move.