This time it was Spain, one of the principal European allies of the U.S.-led war in Iraq and a strong supporter of Israel's efforts against Palestinian terrorism.
Following the suicide bombings in Madrid, which left more than 200 people dead and some 1,400 wounded, even countries opposed to the Iraq war feel exposed to the threat of Islamic terrorism.
Within hours of the bombings, which struck trains in the center and suburbs of the Spanish capital on March 11, security was beefed up in cities across the Continent as news of the carnage left Europe as shell-shocked as the United States was on Sept. 11, 2001.
European leaders called for increased security patrols at major sites, and most countries immediately drafted extra troops and police to guard airports and train stations.
Most poignantly, a whole Continent stood at silence for three minutes Monday in memory of those who lost their lives in the worst terror attack on European soil since the end of World War II.
Across the Continent, Jewish communities wondered how the attacks would affect European attitudes toward the Middle East and the war on terrorism.
Some feared that the Israeli-Palestinian conflict -- and by extension, local Jews -- would be blamed for bringing terrorism to a European capital. Others said the attacks would make Europe more vigilant against the Islamic terrorist threat that Israeli leaders have been warning about for years.
Even as the European Union hastily announced that it would push for stricter measures to combat terrorism -- including demands that all member states accept Europe-wide arrest warrants -- there was substantial political fallout from the Madrid attacks.
The fallout was felt principally in Spain, one of the most vociferous supporters of the war in Iraq. Spanish Prime Minister Jose Maria Aznar saw his Popular Party upset by the opposition Socialists in Sunday's general election.
Aznar's support for the war, and his alignment with a whole range of Bush administration policies in the Middle East -- including strong support for Israel -- had come despite widespread public opposition.
However, some analysts believed the defeat stemmed more from Aznar's initial attempts to shift blame for the Madrid attacks onto the Basque terrorist group ETA, despite mounting evidence showing that the more likely perpetrators were Islamist terrorists.
In recent days, links have been established between the attacks in Madrid and bombings last year in Casablanca and Istanbul that targeted Jewish sites.
Plaudits for the Socialist victory -- as well as the announcement that the new Spanish government is set to withdraw its troops from Iraq -- came from many sources in Western Europe.
As a first stage, though, European leaders are setting about reorganizing how the European Union coordinates the battle against terrorism.
The European Union's Irish president has called for an extraordinary meeting of European justice ministers for Friday with the aim of agreeing on a joint response to the Madrid attacks. The meeting is expected to result in a package of anti-terrorism measures to be approved by European heads of state at a March 25-26 summit.
Also expected is a proposal for the creation of a European commissioner with a specific anti-terrorism portfolio, when the commission is expanded in November as a result of E.U. enlargement.
More controversial is a joint proposal by Belgium, the Netherlands and Austria to revamp the European Union's crime-fighting unit, Europol, to split off anti-terror actions from regular policing of organized crime.
European terrorism experts also will gather Friday for an emergency workshop on "the lessons of Madrid" at the American Jewish Committee's (AJCommittee) new Brussels institute. Experts from Spain, Germany, France and Belgium are expected at the Transatlantic Institute, said Deidre Berger, head of the AJCommittee's Berlin office.
European Jewish leaders told JTA they are adopting a wait-and-see approach on new anti-terrorism measures, saying Friday's meeting of E.U. justice ministers was critical.
However, one senior Jewish leader remarked that he was "already concerned at the reaction of the Europeans, as if they have suddenly discovered that terrorism can strike anywhere and they're completely naked to deal with it."
In Italy, Andrea Jarach, president of the Federation of Italy-Israel Associations, told JTA he was pessimistic about how fallout from the Madrid attacks would impact Israel and Jews.
On the popular level in Europe, "they will say even more than they do now that if the 'Jewish problem' did not exist, there would not be terrorist attacks," he said. "It's terrible, but I fear that the expansion of Al Qaeda activities into Europe will be a further step that cannot but harm the Jews of the world and Israel in particular."
But that same notion -- that the festering Israeli-Palestinian conflict is one reason terrorism has come to the heart of Europe -- could produce some positive results, Berger said.
"I think this could create a dynamic where there will be more interest in Europe in helping to solve the Israeli-Palestinian conflict because many here in Europe see that as one of the critical incitements to terror," she said. "It is a faulty analysis, but we can perhaps use the emotions of the moment to create a new dynamic toward pressuring Arab countries to create a more peaceful climate, engendering a long-term peaceful solution."
Some commentators, though, doubt that the Madrid attacks will lead to major changes in the European Union's Middle East policy.
According to Jean-Luc Marret, a leading expert in terrorism at the Paris-based Strategic Research Foundation, "Europe does not have a security strategy for the Middle East" but would rather pursue its political goals through "incentives to the region in aid and development."
The Spanish election results were "the quickest and most concrete results I have ever seen after a terror attack," Marret said, though he added that he didn't believe that states that opposed the war in Iraq were necessarily exempt from Islamic terrorism.
In Spain, maverick left-wing commentator Pilar Rahola said that the Socialists victors would be wrong to think that an anti-American and anti-Zionist stance would provide insurance against Islamic terrorism.
In Britain, perhaps Washington's closest ally in the Iraq war, insiders predicted that the Madrid attacks and their political aftermath would not change the government's course.
Lord Greville Janner, a veteran politician with the governing Labor Party, told JTA that Cabinet ministers already assume that the United Kingdom is a target for Islamist terrorists.
David Mencer, chairman of the Labor Friends of Israel lobbying group, agreed.
"There is no doubt that the U.K. is a target," he said, noting that London police officials say that "it's not a question of if, but when terrorists strike."
But Prime Minister Tony Blair will not alter the government's course in hopes of lessening the risk of terrorist attack because of his strong personal commitment on matters from Israel to the war in Iraq, Mencer said.
And London has long been quietly supportive of Israel's hard line against terrorists, sources say.
In fact, much of the new policy set for the European Union is likely to please supporters of Israel -- provided it doesn't include nuances distancing Europe from Israel in the hope of reducing the terrorist threat.
Jerusalem likely would warmly receive proposals expected to be presented by the Irish E.U. presidency calling for clearer definitions of terrorist organizations.
That could mean that Hezbollah would immediately be included on proscribed lists in every state in the European Union. Unlike the main Palestinian Islamist groups, the Lebanese Shi'ite organization is not on certain countries' terrorist lists -- but now it's likely that even secondary or charity support groups based in Europe will be banned.
One senior Israeli diplomatic source in Europe said the Jewish state might gain both sympathy and empathy in Europe following the Madrid attacks.
"It's like after Sept. 11, when Americans started to realize what Israelis face everyday," the source told JTA on condition of anonymity.
Nevertheless, he said it was too early to tell if that would translate into a more pro-Israel policy in Europe.
However, the shock of the attacks in the heart of a major European capital has led some countries to issue the kind of statements more commonly heard from Israeli spokesmen.
Visiting a main rail station in central Paris on Sunday, French Prime Minister Jean-Pierre Raffarin said it was necessary to be "particularly vigilant" but "one should not be overtaken by fear, because that would already give a victory to terrorism."
Similarly, the French press, which almost unanimously opposed military intervention in Iraq, described the attacks in Madrid as an attack on all European democracies rather than direct retribution for Spain's support for the war or for U.S. policy in the Middle East.
In Germany, which fiercely opposed the Iraq war, editorialists wrote that giving in to terrorism wouldn't stop the terrorists' demands.
"The withdrawal from Iraq, as the designated Spanish prime minister now has announced, will have an effect comparable to what was produced by the withdrawal of the Israelis from Lebanon," Die Welt said in one editorial.
That resulted in a "bloody increase in Hezbollah attacks and the belief that the Jews 'hang on to life in a cowardly way, while we are prepared to fight and die' -- as it was said at the time, and today again," the paper said.
While some Jewish leaders felt the attacks would further strain trans-Atlantic ties, European Muslim leaders were worried about a backlash similar to the one they felt after Sept. 11.
Haj Thai. Braze, head of the Union of French Islamic Organizations, the leading group on France's recently created Muslim Council and an organization with strong ties to the international Muslim Brotherhood, said European states previously had been careful but now would come closer to U.S. policy.
The United States "is going to say, 'Watch out -- you should support the U.S.A. You've had your March 11 like we had our Sept. 11,'" he said. "I fear for a crusade against Islam and Muslims."
Marret dismissed that argument.
"Ultimately, the Madrid attacks will not have a marked effect on the European conscience like Sept. 11," he told JTA. "We have had catastrophic events on our soil. [World War I and II] marked Europe and changed policy, but not Madrid."
JTA Correspondents Ruth Gruber in Rome, Richard Allen Greene in London, Jerome Socolovsky in Madrid and Toby Axelrod in Berlin contributed to this article.