Two summers ago, U.S. defence secretary Leon Panetta pronounced that his country was "in reach of strategically defeating al-Qaeda." On the first anniversary of the killing of Osama bin Laden, President Barack Obama declared that "the goal I set – to defeat al-Qaeda and deny it a chance to rebuild – is now within our reach."

Not quite, apparently. The recent temporary closing of U.S. embassies throughout the Middle East suggests that the al-Qaeda threat remains alive. Although the U.S. State Department has stated that the organization is "on a path of decline that will be difficult to reverse," the embassy closings suggest such statements to be premature, at the very least.

Just how serious is the al-Qaeda threat? Informed people can disagree, but the Canadian Security Intelligence Service did everyone a favour by convening a workshop on "The Future of al-Qaeda" and then publishing the results1, including three possible scenarios. They ranged from al-Qaeda in decline, as the State Department suggested, to al-Qaeda growing incrementally, to al-Qaeda gaining rapidly in strength.

The incremental growth scenario emerged as the most likely. If that is correct, the organization will remain a threat for a very long time. Al-Qaeda has morphed or sprung offshoots to Saharan Africa and parts of Southeast Asia. It remains resilient in Pakistan and some countries in the Middle East.

Its fighters are now very much involved in the Syrian war, hoping to assist in the overthrow of Bashar al-Assad's regime and replace it with a militant Sunni alternative. And, of course, it has followers and sleeper cells in Western countries who remain a threat, witness to which were the recent arrests of men alleged2 to have been plotting to blow up a train between Toronto and New York.

This very loose network of affiliates persists, despite U.S. drone attacks and other actions that have killed at least 34 key al-Qaeda figures in Pakistan, Yemen and elsewhere. These losses have undoubtedly been disruptive, but the movement grows from the bottom, with new recruits coming from failing states, areas with weak governmental authority, poor economic conditions and, of course, the heavy influence of radical Islam, such as central Yemen, the borderlands of Pakistan, southern Thailand, northern Nigeria or northern Mali.

CSIS published four papers delivered at the conference, but kept the authors' names confidential.

The longest paper, dealing with al-Qaeda Central and al-Qaeda in Iraq, is the most comprehensive and sobering. It concludes that "the long-established nucleus of the al-Qaeda organization has proven itself to be as resilient as it is formidable."

Al-Qaeda's core leadership, the author wrote, "has withstood arguably the greatest international onslaught against a terrorist organization in history." Despite this, the organization has lasted for a quarter of a century. When U.S. troops withdraw from Afghanistan, life will be even easier for al-Qaeda across the border in Pakistan, where its key leaders live and work. The chaos in Syria has presented an opportunity for al-Qaeda to join the fray against an apostate Alawite-controlled regime backed by the Shia forces of Iran and Hezbollah in Lebanon, both enemies of the Sunni jihadis in al-Qaeda.

Western intelligence agencies have become much more sophisticated in identifying al-Qaeda threats. They have prevented attacks and publicized those successes. There may well have been many other successes that the agencies chose to keep quiet. The North American heartland has been protected, a testament to much-improved intelligence practices (and at the cost of a massive loss of public privacy). But there have been attacks in London and Madrid and, of course, in the countries where al-Qaeda and its affiliates operate.

American political scientist Philip Bobbitt has described the struggle against jihadi terror as the "long war." He is right, although "war" suggests a conventional military response, whereas this struggle will be fought more with intelligence than weaponry. It seems likely that it will not end soon, despite what Mr. Obama and others have predicted.