I seem to recall the Irish Government, early-independence (1920s-1930s) was basically run by the military.
You could have Axis leaning, Irish-Junta Government, blinded to the vast disparity of forces by the promises of German Support and the lust for the 32-County Republic.
Britain probably re-arms faster, especially land forces (given that the UK literally have a land border with a fascist, German-leaning state.) 1939 rolls around, Poor Poland gets shat on again, and the UK occupies Ireland before a Counter-Coup can depose the Fascist Government. (I mean, Dublin is Coastal. Hullo Royal Marines!)
UK occupies Ireland, Chamberlain hurriedly gives it back to the Irish before Churchill gets into power again and Annexes it.