Ireland’s parliament made the decision to keep the country neutral during World War II, but the entry of Ireland into the war would have made little difference in the European Theater. However, it is unclear who exactly they would have supported given their tumultuous relationship with Great Britain.
Prior to the outbreak of World War II, Ireland had concluded a long and bloody war with Britain for its independence. Centuries of fighting and English oppression had turned many Irish men and women away from wanting to ally themselves with the crown as the crisis grew.
The people of Ireland overwhelmingly supported Irish neutrality. There were a small minority who supported the idea of siding with the Axis powers, but most Irish who decided to fight served in the Allied military. Most people believed that if they wanted to be considered an independent nation, they should take an independent stance during the war and refused to follow Britain.
Predicating what would have happened if Ireland entered the war officially is difficult, but some conclusions can be made. First, since there were pro and anti-fascist factions within the government, a Civil War might have broken out. The IRA continued to follow its own agenda, which would have further splintered the government and hurt Ireland’s military effectiveness.
If Ireland had sided with the Axis, Britain would have instantly seized Irish ports and airfields. The eventual defeat of the Axis might have led to a re-occupation of the Ireland and more bloodshed.
Ireland would have been more likely to side with Britain, although many would have protested this action, and contributed men to the British army. They had limited naval and air power to begin with, so their contributions would have been meager.
I honesty think that it would not of made a difference. Had they joined the Allied Side, it would of given a slight increase of manpower, but would of not altered the outcome of the War.