Three days after Adolf Hitler committed suicide in 1945, Irish Prime Minister Eamon de Valera visited Germany's envoy in Dublin to pay his condolences.

Until then, de Valera had been considered anti-Axis.

"You can imagine the shock of the Jewish community," scholar Dermot Keogh said in San Francisco last month.

Yet two decades later, Ireland's Jews considered the incident an aberration in the prime minister's overall record. And they honored de Valera by planting a forest of 10,000 trees in Israel in his name.

Such twists mark Keogh's new book, "Jews in Twentieth-Century Ireland: Refugees, Anti-Semitism and the Holocaust." His work is the first comprehensive history of Ireland's Jews.

Though Ireland gave birth to late Israeli President Chaim Herzog and Dublin boasted a Jewish lord mayor, Robert Briscoe, in the 1950s and '60s, Keogh said little attention has been paid to the Jews of Ireland. That's partly because the entire island's Jewish population has been tiny — ranging from about 400 in the 1880s to 5,400 in the mid-1940s to less than 2,000 today.

Keogh, a professor at University College in Cork, became interested in Irish Jews due to his research into Irish history during World War II.

A 53-year-old Catholic, Keogh began studying the treatment of refugees and minorities, such as Jews, Episcopalians, Methodists, Presbyterians and Quakers, in his historically homogeneous country. Today, more than 90 percent of the Irish republic's 3.5 million citizens are Catholic.

Ireland's Jewish history doesn't really begin until the 1800s because so few Jews lived there. When millions of Catholics fled Ireland during the potato famine of the 1840s, Dublin's 25 Jewish families constituted the majority of the island's Jews.

The lack of Jews was partly due to a policy of preventing their immigration, as well as the country's poverty and political instability. But in the 1880s and 1890s, Lithuanian Jews fleeing pogroms were seeking new homelands. By 1901, Ireland's Jewish population grew to about 3,000. That compares to about 150,000 Jews who flooded England during that period.

Soon after Jews arrived in Ireland in relatively large numbers, anti-Semitism sprang up.

Jews were attacked in "radical nationalist" newspapers, Keogh said. Arthur Griffith, founder of the Sinn Fein movement, wrote in 1899 that Jews, Freemasons and pirates were the "Three Evil Influences" of the century and that Jews "detested soap and water."

Jews were also accused of gathering used tea leaves, drying them, mixing them with drugs and selling the compound to the poorer classes as tea. An official investigation in the early 1900s yielded no evidence of such acts. The tea myth, in particular, surprised Keogh.

"People would know a decent cup of tea," said the author, whose Bay Area appearances included a lecture sponsored by the Irish Literature and Historical Society, the Holocaust Center of Northern California and the Jewish Community Center of San Francisco.

One of the more infamous anti-Semitic incidents was the Limerick "pogrom" in 1904. Though no one was seriously injured, rioting occurred. And the term "pogrom" has stuck.

The incident began when a priest used the pulpit to attack Jews. He called Jewish peddlers and merchants "leeches" who were sucking the blood of the Irish by overcharging or tricking the poor. The priest called for a boycott of Jewish merchants, and the town complied.

Within a few years, virtually all of Limerick's 25 Jewish families and the rabbi had left.

Keogh's book focuses on anti-Semitic mindsets and acts. Still, he concludes that anti-Semitism was never an "operational principle" among the Irish policy-making elites.

"I feel there was an affinity to the underdog. The political leadership wouldn't have accepted the notion of anti-Semitism," he said. "And you couldn't say that anti-Semitism was a dominant part of Irish culture."

In 1937, Irish leaders added to the constitution recognition of Judaism as a minority religion and a guarantee of freedom from discrimination. By contrast, Germany passed its anti-Jewish Nuremberg Laws two years earlier.

Ireland did have a "very restrictive" immigration policy for Jews trying to flee the Nazis; as few as 60 Jews were allowed in during the war years, according to the book.

Still, only one Irish Jew is known to have died in the Holocaust. Esther Steinberg, raised in Dublin, was living in Belgium with her husband and young son when the Nazis invaded. The family went into hiding. But they were rounded up, sent to Auschwitz and killed immediately.

The prime minister's decision to pay a condolence call to one of Hitler's underlings shocked not only Jews. One of his government ministers reportedly got down on his knees and begged de Valera not to go. But De Valera had a good working relationship with the envoy, Keogh said, and perhaps did it out of personal loyalty.

"He did it probably because he felt it was protocol."

However, Keogh added, the act was "totally out of character" for de Valera. "I'm still at a loss to know why he did it."