The very fact that al-Qaida was forced to concentrate in Yemen tacitly but very powerfully reflects the major setbacks it has suffered in Iraq over the past year and a half and also underlines its long-term strategic failure in Saudi Arabia over the past six years. For all the wishful thinking and miscalculations recorded in the Bush administration's catastrophic occupation of Iraq over the past five and a half years, the far more successful and enlightened counter-insurgency policies of outgoing U.S. Gen. David Petraeus has dealt al-Qaida enormous and unanticipated setbacks.

At the center of the U.S. success has been Gen. Petraeus' recognition -- in contrast to all the U.S. military commanders and Pentagon policymakers who preceded him in Baghdad -- that working with the Sunni Muslim Arabs of central Iraq as friends was vastly more effective than treating them all as bitter enemies.

Petraeus' successor as ground forces commander, Gen. Raymond Odierno, has not in his previous tours of duty in Iraq shown anything like the same flexibility and understanding of local culture and politics. But it is very much to be hoped that he will learn and apply the appropriate lessons from Gen. Petraeus' example.

It would, however, be a very bad mistake to shrug off the Sanaa bombing as a last, desperate parting shot by an al-Qaida that is on the rocks. For al-Qaida has previously shown that it regards Yemen as a country to carry out "trial run" terror attacks before trying to replicate them on a far more ambitious and widespread scale around the world.

The effective sinking of the USS Cole in Aden harbor in Yemen in 2000 proved to be an unheeded warning sign that the organization was gearing up for its notorious Sept. 11, 2001, attacks on the American mainland. The national security apparatus of the Clinton administration proved catastrophically negligent at the time in not recognizing the USS Cole attack as the wake-up warning that it in truth was. Outgoing U.S. President George W. Bush and his successor, whether it be Republican presidential candidate Sen. John McCain or his Democratic opponent Sen. Barack Obama, would do well to take Wednesday's attack far more seriously than their predecessors did the assault on the Cole.

The evils that have proliferated from the U.S. invasion of Iraq have graphically proved that neo-colonialism and military aggression are no cures for the evil of terrorist extremism: they only serve to aggravate the problem. But hitherto obscure backwaters like Afghanistan, Yemen and Somalia cannot be left alone in a state of malign neglect either: When that happens, al-Qaida and its ideological bedfellows are left free to plot new outrages against the mainstream Muslim and Western worlds.