More than 3,600 people from the south of Ireland - now the Republic of Ireland - were killed, despite the country being officially neutral.
Thanks to the research by University of Edinburgh historians, these thousands of forgotten war dead will be added to the Roll of Honour unveiled today(Friday).
They join the nearly 4,000 killed in action from Northern Ireland who will also be honoured at the ceremony at Trinity College in Dublin.
Yvonne McEwen, from the university's Centre for the Study of The Two World Wars, said that the research was a major step in portraying the full picture of Ireland's contribution to the Second World War.
She said: "This is a historical enquiry which needed to be undertaken to help tell the story of the significant role of the Irish volunteers which, to date, has largely been untold.
"There is a moral imperative to record the major contribution of those Irish men and women who served and died."
The new data represents an attempt to shed new light on the role of Irish forces during World War Two.
The research reveals that in the British army alone, there may have been as many as 100,000 people from both southern and Northern Ireland serving in the British Army.
Ireland did not fight as a nation during the Second World War, which it referred to as "The Emergency".
Despite this, more than 100,000 men and women from all over the country joined the British Army to fight the Nazis.
Prof McEwen said: "Many feared that Hitler would not keep his promise to respect Ireland's neutrality, however for most it was simply a way out of a desperately poor background.
"The prospect of fighting abroad was exciting and by joining the British army, many Irish were able to escape from their economic binds."