How the NYPD Foiled the Post-9/11 Terror Plots

New York’s police commissioner has 1,200 staff members devoted to counterterrorism, at home and abroad.

A specter has haunted the New York Police Department during this week’s torrent of 10th anniversary commemorations of 9/11—the 13 terrorist plots against the city in the past decade that have failed or been thwarted thanks partly to NYPD counterterrorism efforts.

Police Commissioner Raymond W. Kelly and his 50,000-strong department know that the 9/11 gatherings are an occasion not only to reflect on that terrible day. They’re also a prime target for al Qaeda and other Islamist extremists who long to convince the world, and perhaps themselves, that they’re still capable of killing in the name of their perverse interpretation of Islam.

Commissioner Kelly allocates some $330 million of his $4.6 billion annual budget and 1,200 of his staff to counterterrorism. He and his staff, not surprisingly, spent the week bolstering security at the remembrance gatherings throughout the city. On Wednesday, he came to the Manhattan Institute to tout the NYPD’s counterterrorism record and defend his department against press allegations that his intelligence division has been spying illegally on Muslims and infringing on their privacy and civil rights.

The police have to factor terrorism into “everything we do,” Mr. Kelly said. If that means following leads that take NYPD undercover detectives into mosques, Islamic bookstores, Muslim student associations, cafes and nightclubs, so be it. Mr. Kelly vowed to continue stationing liaisons in 11 cities abroad to “ask the New York question”—much to the occasional chagrin of the Federal Bureau of Investigation and the CIA.

It was an undercover officer in an Islamic bookstore who helped stop Shahawar Matin Siraj, a homegrown Muslim extremist and self-professed al Qaeda admirer, from bombing the Herald Square subway station during the 2004 Republican convention, Mr. Kelly said. Another undercover officer prevented homegrown terrorists Ahmed Ferhani, 26, and Mohamed Mamdouh, 20, from bombing a Manhattan synagogue and trying to “take out the entire building.”

Would he continue sending NYPD officers across the Hudson into deepest, darkest New Jersey? Yes, he declared, if that was what was needed to keep tabs on the likes of Carlos Almonte and Mohammed Alessa—al Qaeda sympathizers arrested en route to Somalia at JFK Airport in 2010 “who were determined to receive terrorist training abroad only to return home to kill us here.”

Michael Sheehan, a former NYPD deputy commissioner for counterterrorism, says that the NYPD has succeeded thanks to its collection and sharing of domestic and foreign intelligence through “humint” (human sources) and “sigint” (signals intelligence) such as electronic intercepts and the monitoring of Internet, cellphone and other communications. Tip-offs from concerned family or community members have also been vital.

Sigint was key in disrupting at least two of the most serious al Qaeda plots targeting New York since 9/11: the 2006 “Liquid Bomb Plot,” or “Operation Overt,” in which 25 British citizens of Pakistani descent targeted some seven transatlantic commercial flights from London to North America; and Operation Highrise, an attempt to use suicide bombers to blow up New York City subways in 2009.

The homegrown Islamist in that plot was Najibullah Zazi, an Afghan immigrant with al Qaeda ties who grew up in New York City and staged his operation from there and Colorado. In Zazi’s case, investigators say, officials were initially tipped off by the intercept of an email he sent from Colorado to an address in Pakistan that was associated with another group of terrorists who had been arrested earlier that year in Manchester, England.

The “link man,” or coordinator in Pakistan, writes Mitchell D. Silber, director of Intelligence Analysis for the New York Police Department, in his forthcoming book, “The Al Qaeda Factor,” was corresponding with operatives in three different al Qaeda plots. Zazi’s New York subway plot took off only after he contacted the coordinator, identified only as “Ahmad,” and informed him that the “wedding,” or suicide operation, “was ready to proceed,” writes Mr. Silber.

Another serious plot that was disrupted thanks to Internet intercepts was a 2006 scheme by Assem Hammoud, a 31-year-old Lebanese al Qaeda member, and several other still unnamed Islamists—all overseas—to flood Lower Manhattan by setting off explosives in the PATH railway tunnels under the Hudson River. While no arrests in America were made, several suspects have been detained in Lebanon and other Arab states.

Mr. Silber argues that humint has proven even more valuable than sigint in detecting and thwarting homegrown threats—the fastest-growing category of militant Islamist terror. This explains Mr. Kelly’s determination to preserve the NYPD’s vast intelligence capabilities, even if he’s forced to scale back elsewhere in the department due to budget cuts.

With Osama bin Laden dead and al Qaeda under pressure, some terrorism experts argue, as does Peter Bergen, author of the book “The Longest War,” that al Qaeda, or at least its “core,” “no longer poses a national security threat” to America “that could result in a mass-casualty attack anywhere close to the scale of 9/11.”

Mr. Kelly isn’t buying it. He’s fixated on the recent jump in homegrown extremist plots throughout the country—to 10 in 2009 and 12 in 2010 from four in 2007 and just one in 2005. The increase, says John Miller, a former deputy director for analysis for the Director of National Intelligence, is most likely due to the influence of Anwar al-Awlaki, the Yemeni-American cleric now hiding in Yemen whose stirring Internet sermons have inspired many of the would-be jihadis detained in recent plots.

Mr. Kelly also knows that in too many cases, New York has been lucky. Faisal Shazad, a middle-class Pakistani–American resident of Connecticut, failed last year to detonate a bomb in Times Square only because he received too little training in Pakistan.

Mr. Kelly calls the killing of bin Laden “success with complications.” Those include the numerous references to New York found in his documents in Abbottabad, all of which suggest that bin Laden never abandoned his dream of striking the city again. The discovery on Thursday night of a specific and “credible” al Qaeda linked plot tied to the 9/11 commemorations suggests that Mr. Kelly’s concern is justified.

This piece originally appeared in The Wall Street Journal