The Irish should fight back as well as call for foreign volunteers. This will provide them with added man power and financing. It will also provide an opportunity for nationalists from across Europe to train, hone skills, and demonstrate resolve. The fighting will forge unbreakable bonds amongst the men.
If they succeed in Ireland, this hypothetical foreign legion could relocate to the next Euro country with enough balls to protect itself.
America has a whole bunch of "Irish-Americans." If a figure like Connor calls on them to come protect the homeland, I can guarantee you would get another significant boost in numbers.