WAS THE MARCH 11, 2004, attack on Madrid's commuter trains an al Qaeda operation? More than three years after 191 civilians were killed and almost two thousand more injured by ten backpack bombs planted by Islamic radicals, the answer to such a simple question remains clouded. Just this past Wednesday, as the verdicts of 28 of the accused plotters were read by a Spanish court, we were reminded how murky this issue has become.

Few, if any, in the mainstream American press referred to the plotters as agents of al Qaeda. Instead, much of the coverage was similar to the Washington Post's description:

Spanish authorities said the plot was organized locally by a cell of Islamic ideologues that had no direct connections to al-Qaeda or other international networks. But they were unable to clarify who directed the conspiracy or gave the final orders for the attacks.

The Post does not deserve special scorn for its coverage of this issue; its characterization of the plot is fairly typical. Indeed, the NYPD offered a similar assessment in a recent report titled "Radicalization in the West: The Homegrown Threat." In that report, the NYPD's intelligence analysts described the 3/11 attack as one of several, also including the July 7, 2005, bombings in London, which were merely inspired by al Qaeda's ideology. "Rather than being directed from al Qaeda abroad," the NYPD surmised, "these plots have been conceptualized and planned by 'unremarkable' local residents/citizens who sought to attack their country of residence, utilizing

Simply put, there are many who believe that 3/11 was not committed by the same network of hardened terrorists that struck America exactly 911 days prior in Washington and New York.

Such a hypothesis sounds plausible on its face. But it is entirely wrong.

To fully recount the threads of evidence tying the 3/11 plotters to al Qaeda would take dozens, if not hundreds, of pages. Fortunately for us, an authoritative review of this evidence has already been written. Chapter 11 of counterterrorism expert Lorenzo Vidino's seminal 2006 book, Al Qaeda in Europe, is devoted to the Madrid train bombings. It is impossible to square the well-sourced compilation of details Vidino provides with the notion that al Qaeda was not responsible for the 3/11 attack. Highlights from Vidino's book, as well as dozens of press accounts, make al Qaeda's hand clear.

One of the key conspirators at the heart of the recently concluded Spanish trial was a Moroccan man named Jamal Zougam. Zougam was one of only three defendants convicted of mass murder. Eighteen other defendants were convicted on lesser charges and seven were acquitted in full. Zougam procured the cell phones used to detonate the backpack bombs used in the operation and some eyewitnesses saw him place at least one of the bombs himself.

Although you will not read it in the press, Zougam was clearly an al Qaeda agent. For years he served a Syrian named Imad Yarkas. Known by his nom de guerre, Abu Dahdah, in jihadist circles, Yarkas is a notorious al Qaeda chieftain. Yarkas's terrorist career began in the early 1980's as a member of the Syrian Muslim Brotherhood, an Islamist terrorist group then sponsored by Saddam Hussein, and by the 1990's he had become one of Osama bin Laden's primary emissaries in Europe. There is no disputing Yarkas's al Qaeda affiliation; he was thrown in jail shortly after the September 11 attacks and later convicted on terrorism charges.