The prospects of Irish Home Rule being achieved spurred furious resistance on the part of unionists in Northern Ireland. In this they were abetted by the leadership of the Conservative Party even to a degree that went beyond parliamentary or constitutional opposition. A new leader had taken over the Conservative Party in the person of Andrew Bonar Law. He reflected a significant change in the party, as his predecessor, Arthur Balfour, had an extraordinary pedigree as a son-in-law of the last Conservative prime minister, Lord Salisbury, a descendant of the Elizabethan favorites, the Cecils. Bonar Law, on the other hand, was a Canadian-born Scot, whose fortune was based on industry. He represented the new influence of business and industry over the Conservative Party, hitherto dominated by hereditary influences and landed wealth. Furthermore, he was a Presbyterian, whereas the party had always been identified with the Church of England. This made him more responsive to the Presbyterian and industrial spirit of Northern Irish unionism and ready to endorse extra-legal action to block Home Rule. At an anti-Home Rule demonstration at Blenheim Palace in July 1912, he suggested that "there are things stronger than parliamentary majorities," as he promised that there was "no length of resistance to which Ulster can go in which I would not be prepared to support them, and in which, in my belief, they would not be supported by the overwhelming majority of the British people."
This clear invitation to turn to extra-constitutional action was taken up by the Ulster Unionists in September of that year when nearly half a million of adult males supporters signed a Solemn League and Covenant to use all necessary means "to defeat the present conspiracy to set up a Home Rule Parliament in Ireland," and should such be forced on them "to refuse to recognize its authority." A few months later, in January 1913, the Ulster Unionist Council, the governing body of the Unionist Party in Ulster, approved the formation of
The Ulster Volunteer Force, a paramilitary organization of 100,000 members whose component branches had already been in the process of formation among the various Orange lodges.
A major figure in Ireland in the unionist resistance to Home Rule was Edward Carson, a Dublin-born barrister, member of parliament for Trinity College, and leader of the Unionist Party in Ireland, renowned for his legal competence, including especially his successful and devastating cross-examination of Oscar Wilde in the libel suit that led to his ruination. Carson was generous in his attitudes toward concessions to Catholics on issues short of repeal of the union, but he was ultimately governed by his commitment to the maintenance of the union of the entire island of Ireland with Britain. In other words, Carson was an Irish Unionist, anxious that the whole island of Ireland be united with Britain. The other major figure in the opposition to Home Rule was James Craig, an Ulster Presbyterian from a family that made its fortune from distilling. A member of parliament from County Down, his primary political commitment was to preserve the Ulster he knew, that was, one of Protestant predominance and linked to Britain.