The barbaric terrorist attacks in London Thursday, which claimed at least 37 lives, are a direct assault on the Anglo-U.S. alliance, the engine of the global war on terror.

An al-Qaeda splinter group calling itself the Secret Group of al-Qaeda's Jihad in Europe already has claimed responsibility for the blasts. Its motives are clear. With Britain universally acknowledged as America's closest ally, an attack on London is no different from an attack on Washington or New York.

By striking London, the group hopes for a three-pronged propaganda success. First it plans to disrupt the Group of 8 (G-8) meeting, a symbol of the most powerful Western leaders in the world.

Second, it hopes for the "Spanish effect" to alienate the British public from its government, as was so successful in Madrid. It is here that the terrorists are bound to fail, for they have underestimated both the strength and resolve of the British people, as well as the durable ties that bind the U.S. and the U.K.

A third goal of the attack is to fracture the Anglo-American partnership in Iraq, by making the price of cooperation with the United States too costly to bear. Today's cowardly bombings are closely modeled on the Madrid attacks of March 2004 and are aimed especially at forcing a British withdrawal of its 8,000 troops from Iraq. Here again, the Anglo-American alliance stands as the bulwark of Western civilization. An immediate withdrawal from Iraq would be a cataclysmic defeat for the West and an immense victory for Abu Musab Al-Zarqawi and his murderous cohorts.

What the terrorists fail to understand is the British bulldog tradition of rising to meet every challenge. What they also fail to comprehend is that when the chips are down, the U.S. and U.K., like Butch Cassidy and the Sundance Kid, come out shooting together. This terrible atrocity will not alter these fundamental facts; rather they will merely strengthen the Anglo-American resolve.

The terrorists responsible for this outrage will not succeed in changing British policy in Iraq. If anything, the attack will only increase the determination of the British government to stay in Iraq and will likely result in an expansion of British troop levels in the country. Prime Minister Tony Blair is no Jose Luis Rodriguez Zapatero.

Britain is at War

The common Anglo-American operational response to the bombing is obvious. There must be immediate retaliation by the U.S. and U.K. -- the war must be taken to the terrorists. Whoever has harbored, funded, aided or abetted these terrorists must be held to account. If any state has played a role in these attacks, there must be consequences.

Special forces operations, strategic air strikes, and the targeted elimination of terrorist leaders must all be on the table, in addition to a meticulous hunt for the al-Qaeda sleeper cells operating in London and major cities across Europe. No quarter should be given to those who have murdered innocent civilians. Make no mistake: This is an epic war between civilization and the barbaric forces that wish its destruction.

At Britain's hour of need, the United States will stand shoulder to shoulder with her British allies, who are bloodied but unbowed. The terrorists' fatal conceit is similar to that of the Kaiser, Hitler and Stalin: underestimating the power and determination of the Anglo-Saxon peoples. This is a war that may last for decades, but will ultimately be won by the two nations that stand at the forefront of defending freedom and liberty on the world stage.

Nile Gardiner is visiting fellow in Anglo-American security policy, and John Hulsman is research fellow in European affairs at the Heritage Foundation.