Irregular War, urban insurgency, political violence.
Europe, Latin America, Ireland, United Kingdom, United States
Arming Irish Revolution: Gunrunning and Arms Smuggling in Ireland, 1911–1922 (University Press of Kansas, contracted)
Ground Truths: British Army Operations in the Irish War for Independence (Irish Academic Press, 2013), expanded with commentary; editor.
Ambushes and Armour: The Irish Rebellion 1919–1921 (Irish Academic Press, 2010)
The Anglo-Irish War, 1916–1921: A People’s War (Praeger, 1999).