Eoin MacNeill (1867-1945) was a co-founder of the Gaelic League alongside Douglas Hyde as well as later becoming chief of staff of the Irish Volunteers, founded in reaction to the Ulster Volunteers. He was also a highly respected professor who wrote extensively about Irish history and also taught early Irish history at University College Dublin (UCD). He is most infamous however in Irish history for issuing the controversial countermanding order that prevented thousands more Volunteers joining the Easter Rising of 1916.
The North Began (1913)
Phases of Irish History (1920)