Military Cancels – Northern Ireland. 
MILITARY CANCELS Northern Ireland
Collecting commemorative cancels from the British military in Northern Ireland can be an interesting area. These cancels are created to commemorate an event, often the closure of a base or the disbandment of a unit.
Another interesting are is finding American military mail from units stationed there in WWII in preparation for the invasion of Nazi-held continental Europe. Several divisions were based there in addition to Army Air Force units, and Naval forces transiting Londonderry en-route to and from convoy escort duty on the North Atlantic. See “American Military in Ireland – WWII”. Lest we forget them, there were Americans manning blimps and destroyers in Ireland during WWI.
Mail and cancels of the military arms of the Republic are discussed as a separate topic.
While there is no specific sources or catalog of such cancels, they are often listed in Gibbon’s Stamp Monthly.