On July 18, 1994, a van loaded with 275 kilograms of explosives was detonated in front of the Jewish Community Center in Buenos Aires, Argentina. It caused the complete collapse of the building, killing 85 people and injuring more than 300. The Lebanese Shi’ite militia, backed by Iran, which for years had been fighting Israel on the state’s northern border, had opened a second front, this time against the Jewish people. The attack was masterminded by Imad Mughniyeh, Hezbollah’s chief of operations, who was assassinated in Syria in 2008.

Palestinian terrorists had already attacked Jewish targets abroad, back in 1982: Six people were killed and 22 injured in August of that year, in an attack on the Jewish restaurant Chez Jo Goldenberg in Paris. In a similar attack on worshipers at Rome’s Great Synagogue two months later, a 2-year-old boy was killed and 34 people were wounded. Now Hezbollah let it be known that it too was targeting the Jewish people.

After September 11, Al-Qaida joined the ranks of terrorist organizations targeting Jews in various locations around the world. On April 12, 2002, an explosives-filled truck loaded was detonated in front of the synagogue on the Tunisian island of Djerba, killing 19 people and injuring more than 30. On May 16, 2003, in attacks on Jewish targets in Casablanca, Morocco, 33 people were killed and more than 100 were wounded. And on November 15, 2003, trucks carrying explosives slammed into the Bet Israel and the Neve Shalom synagogues in Istanbul, Turkey, killing 27 and injuring more than 300. All these attacks were carried out by units associated with Al-Qaida.

Israeli intelligence and intelligence organizations throughout the world keep a close watch on the activities of Hezbollah, Al-Qaida and Palestinian terrorists. The information they have collected has foiled a number of planned attacks on Jewish targets. It is a constant battle of wits, and the expectation is that most, but not all, such attacks can be prevented. It is a quite a different matter when the attacks are launched by individuals, “lone wolves,” on their own initiative, rather than being planned by an organization.

This is what happened in Toulouse, France, at 8 A.M. on March 19, 2012. Mohamed Merah, a French citizen who had been radicalized during two sojourns in Afghanistan and Pakistan, rode up to the Ozar Hatorah Jewish day school on a motorcycle and opened fire, killing three children and a rabbi. It seems that he was acting on his own.

The recent incident in Brussels bears a frightening similarity to the murder in Toulouse. On May 24, Mehdi Nemmouche, a French citizen who fought with jihadist forces in Syria, approached the Jewish Museum of Belgium and opened fire with an automatic weapon, killing three people and critically wounding a fourth, who died in hospital on June 6. Nemmouche was arrested a week after the attack in the French city of Marseille. It is not yet known whether he acted alone or received assistance from others in Belgium.

It is estimated that 2,000 citizens of western European countries have traveled to Syria to join one of the many jihadist militias involved in that country’s civil war. The exact number of American citizens who have done the same is not known, but it surely numbers in the hundreds. Upon their return, after being indoctrinated in fanatical Islam and receiving weapons training, they constitute a danger to Jews wherever they go, stalking Jewish targets of opportunity.

It is next to impossible for the intelligence community to obtain advance information on what are almost random acts by single individuals. Therein lies the danger to Jews in many parts of the world, a danger which may actually be greater than that posed by Hezbollah and Al-Qaida. The main onus for locating and monitoring these jihadist converts after their stay in Syria is on the police and security services in the countries to which they return. Had this been done in the cases of Merah and Nemmouche, lives would have been saved. That is the challenge facing these agencies now, if further murders are to be avoided in this war against the Jews that the jihadists have declared.