On May 25, 1921 the IRA launched one of its largest and most audacious operations when it attacked Dublin's Custom House, the heart of the British administration in Ireland.

Many still view this as a military failure that destroyed the IRA's Second Battalion in Dublin. But, over the last number of years, historians Liz Gillis and Mícheál Ó Doibhilín have, based on their extensive research, challenged this view, arguing that the operation was, in fact, a success which probably helped bring about a truce and the subsequent Treaty negotiations.

Now Liz Gillis, historian and author of six books on Ireland's early 20th century revolutionary period, tells this story in detail, including the planning and consequences, using much information that is new, as well as the recollections of those who were there.