AS THE IRAN DEBATE has progressed, a somewhat disturbing trend has emerged in which those who have previously warned of the dangers posed by Tehran have now sought to ignore or downplay these earlier statements. Perhaps this is because they are fearful of the prospect of a military confrontation with Iran and do not wish to be seen as supplying anything resembling a casus belli. This is essentially the reverse of what the Bush administration is accused of doing during the run-up to the war in Iraq, with information being presented selectively for the purpose of downplaying the Iranian threat. This seems unwise.

An honest assessment of the Iranian threat is necessary, beginning with the Iranian regime's role in the events leading up to September 11. According to the text of the 9/11 Commission report:

Khallad and other detainees have described the willingness of Iranian officials to facilitate the travel of al Qaeda members through Iran, on their way to and from Afghanistan . . . Such arrangements were particularly beneficial to Saudi members of al Qaeda.

. . . In October 2000, a senior operative of Hezbollah visited Saudi Arabia to coordinate activities there. He also planned to assist individuals in Saudi Arabia in traveling to Iran during November. A top Hezbollah commander and Saudi Hezbollah contacts were involved.

. . . In November, Ahmed al Ghamdi flew to Beirut, traveling--perhaps by coincidence--on the same flight as a senior Hezbollah operative. Also in November, Salem al Hazmi apparently flew from Saudi Arabia to Beirut.

In mid-November, we believe, three of the future muscle hijackers, Wail al Shehri, Waleed al Shehri, and Ahmed al Nami . . . traveled in a group from Saudi Arabia to Beirut and then onward to Iran. An associate of a senior Hezbollah operative was on the same flight that took the future hijackers to Iran. Hezbollah officials in Beirut and Iran were expecting the arrival of a group during the same time period. The travel of this group was important enough to merit the attention of senior figures in Hezbollah.

. . . In sum, there is strong evidence that Iran facilitated the transit of senior al Qaeda members into and out of Afghanistan before 9/11, and that some of these were future 9/11 hijackers. There is also circumstantial evidence that senior Hezbollah operatives were closely tracking the travel of some of these future muscle hijackers into Iran in November 2000.

The Commission's final report noted that it had found "no evidence that Iran or Hezbollah was aware of the planning for what later became the 9/11 attack," but closed that section of the report by stating that, "We believe this topic requires further investigation by the U.S. government"--a position which was also taken by the Commission's co-chairs, Thomas Kean and Lee Hamilton, in interviews following the publication of the final report. Kean said that "We know of a relationship [between Iran and al Qaeda]; how deep that relationship is . . . that's really going to require more research." Hamilton agreed, saying that the relationship "really does need more investigation."