IT ranks as one of the most controversial decisions every taken by a Taoiseach.
When Eamon de Valera paid a visit to the Nazi envoy to Dublin in 1945 to sign a book of condolence for Adolf Hitler, his actions sparked international anger and remained as one of the most infamous incidents of his life.
New research has shown Mr de Valera fully expected the furore he created when he called on the German ambassador Eduard Hempel, to "express condolences" after Hitler's death was announced on May 2.
He never publicly explained the rationale behind his visit but previously secret papers in a new Royal Irish Academy book -- 'Documents on Irish Foreign Policy 1941-1945' -- show his thoughts following the incident.
"I had expected this," Mr de Valera wrote. "I acted correctly and I feel certain wisely."
Mr de Valera said he could have feigned a "diplomatic illness" but he would "scorn that sort of thing".
"So long as we retained our diplomatic relations with Germany, to have failed to call upon the German representative would have been an act of unpardonable discourtesy to the German nation and to Dr Hempel," he said in a letter.
He said he was "certainly" not going to add to Dr Hempel's humiliation "in the hour of defeat".
"I had another reason," his letter says. "It would establish a bad precedent. It is of considerable importance that the formal acts of courtesy should not have attached to them any further special significance, such as connoting approval or disapproval of the state in question or of its head."
However, the new book instead argues Mr de Valera's justification "rings hollow" and the decision was an "ill-conceived, infamous visit" that damaged Ireland's international position following the war.
Another memorandum reveals the US envoy in Ireland David Gray complained that President Douglas Hyde's secretary Michael McDunphy had also visited Dr Hempel following Hitler's death.
Mr Gray complained that Mr McDunphy had not visited him following the death of President Franklin Roosevelt in April 1945. Mr McDunphy argued that after Hitler's death, Berlin was occupied and there was no one to whom Mr Hyde could express condolences as had happened in the US following Mr Roosevelt's death.