The thing that caught our eye in the plot to blow up John F. Kennedy International Airport and its oil lines concerns a detail in respect of the arrest of one of the key Guyanese suspects. It was the fact that the former member of the Guyanese legislature who was fingered in the plot, Abdul Kadir, was arrested in Trinidad on his way to Caracas, Venezuela. According to Mr. Kadir’s wife, who was quoted in the Guyanese press, he was there to pick up an Iranian visa that would enable him to attend an Islamic conference in Tehran.

No doubt we will learn more about this plot as the weeks go on. Our sense of the intelligence community is that it is reserving its judgment, though clearly congratulations are in order for Commissioner Kelly, the United States attorney in Brooklyn, Roslynn Mauskopf, and the other officials involved in breaking this case. But our attention has been riveted for some time on growing evidence that the Iranian regime has been moving aggressively to gain influence in our hemisphere, and the big surprise in the latest case is only that it took so long for something to develop.

It was back on January 16 that we issued an editorial in these columns called “Enemy in Our Back Yard,” reporting on how left-wing, anti-American leaders in Latin America have been rolling out the red carpet for President Ahmadinejad. At the time, Mr. Ahmadinejad was visiting Latin America for the second time in four months. In Venezuela, he was received at the airport by President Chavez. “Welcome to Venezuela, where Iran is beloved,” the Caracas daily El Universal quoted Mr Chavez as saying. “We give welcome to a distinguished leader, the leader of a heroic people and of a revolution kindred to the Venezuelan revolution: the Islamic revolution.”

Our editorial noted that the two promptly retired to Mirafloras, the presidential palace, to sign off on “at least 29 memorandums and letters of intent” and “also reiterated that they would push for OPEC production cuts.” That was reported in El Universal. The Associated Press reported they announced plans for a $2 billion joint fund to finance projects that would thwart American domination “This fund, my brother, will become a mechanism for liberation,” Mr. Ahmadinejad said to Mr. Chavez during the announcement.

The Iranian president then continued to Nicaragua, where, according to Iran’s state-owned Islamic Republic News Agency, he was awarded two state medals by Nicaragua’s newly inaugurated president and America’s old foe, Daniel Ortega. Agreements were signed to establish diplomatic relations and open embassies in Managua and Tehran, according to El Nuevo Diario in the Nicaraguan capital. Visiting a Nicaraguan slum together, Mr. Ahmadinejad called Mr. Ortega a “symbol of justice,” and Mr. Ortega promised to “fight for … the defense of our sovereignty.”

The AP also reported at the time that Mr. Ahmadinejad was present at the inauguration of Ecuador’s new left-wing president, Rafael Correa, who has promised to shut down an American airbase there. This led us to observe that until recently, Mr. Chavez and his fellow Latin American leftists were an annoyance for advocates of free trade and good governance. But by allying themselves with Islamic extremists, they’ve become a great deal more dangerous. Witness what we learned during the Cuban missile crisis.

While the Iranian entente with anti-American regimes in South America and the Caribbean was economic in nature, we predicted that eventually it would become military in nature. We noted that in the last several years Venezuela has been making billions of dollars in arms purchases, including both small arms and more serious weapons like the Sukhoi Su-30 Russian fighter jets and Russian-made attack helicopters. There is also increasing troop movement among the left-wing Latin American states. The military ambitions of Messrs. Chavez, Ortega, and Ahmadinejad spell trouble.

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This is the backdrop against which we view this latest coup of law enforcement. The case is still early. As with any criminal case, the burden is always on the prosecution; defendants are not required to prove anything. But the vigilance we have seen in the past few days couldn’t be more important. We said it in January, and it bears repeating. Blocking Islamist maneuvering in Latin America needs to be put at the top of the priorities for American foreign policy in the coming months. And our authorities need to understand the phenomenon of what is called the Red-brown coalition, red meaning leftist and brown meaning fascist. It’s been a feature of the modern struggle since the Hitler-Stalin pact.

Back on the eve of the World War II, there were some on the left who were prepared to look away. But only briefly. This mixture proved extraordinarily combustible. The existence of a Marxist-Islamist scheme in Latin America – for that is what we see twixt Messrs. Ahmadinejad and Chavez and Ortega — is every bit as dangerous as the analogous scene was between the Nazis and the Soviet Communists. Mayor Bloomberg, Mr. Kelly, Ms. Mauskopf, and their colleagues at the Federal Bureau of Investigation and other agencies have given us great law enforcement in New York. Understanding the way in which this danger is being nursed in our back yard will, we predict, become a matter of ever greater urgency.