[1][2] Initially drawing its membership from branches of the Liverpool-based National Union of Dock Labourers, from which Larkin had been expelled, it grew to include workers in a range of industries.

The ITGWU was at the centre of the syndicalist-inspired Dublin Lockout in 1913, the events of which left a lasting impression on the union and hence on the Irish Labour Movement.

In turn, William O'Brien became the union's leading figure, and ultimately served as general secretary for many years.

Throughout World War I, the ITGWU consistently opposed Irish belligerence, and staunchly supported the advanced nationalist cause.

In fact, ITGWU members, in the uniform of the Irish Citizen Army, played a leading role in the Easter Rising, while the Transport Union led a national strike that crippled an attempt to introduce conscription to Ireland in 1918.