"It is not generally known that after the fall of France in 1940, the line of the Upper Bann linked with the Newry canals through to Carlingford Lough became a defensive position in case of German landings in the Republic of Ireland. This line of defence through from Lough Neagh to Carlingford Lough was to safeguard the east of Northern Ireland from German attack. To this end, the bridges at Portadown were mined and left ready for instant demolition. ".
from:
http://www.geocities.com/craigavonhs/rev/luttoninlandport.html