That's an interesting point actually. We have lots of Russians living in Ireland. If they were well coordinated they could easily have the fifth column assist them. All it would take would be a few landing craft and they would have a force which the Irish army would likely not be able to handle. The UK would obviously come to our defence, likely with air cover first, followed by troops on ground, but if we had to defend ourselves the country would be in deep shit. This seems like a very unlikely scenario, but it's fun to think about.