As the fifth anniversary of the invasion of Iraq approaches, the United States has proved her critics wrong -- again. The U.S.-led surge in Iraq has been a remarkable success, and the fledgling democracy is no longer descending into civil war. The ballot box and the rule of law are rapidly replacing terror, fear and intimidation as the norm. Even the BBC reported in January that Al-Qaeda in Iraq had been "reduced by 75 percent."

Since the surge was launched over a year ago with the phased introduction of an additional 30,000 American troops, overall terrorist attacks in Iraq are down by more than half, and civilian deaths have fallen by nearly two thirds. Bombings in Baghdad are now at their lowest level since 2005. Al-Qaeda is on the run across large swathes of the Sunni heartlands, with previously warring Iraqi factions now uniting against the foreign Jihadists who have ravaged their country. Last October alone no less than 40 al-Qaeda leaders were killed or captured. Such is the improvement in the security situation that Iraqi security forces are now responsible for nine of the nation's 18 provinces.

The surge campaign has demonstrated that the United States is capable today of fighting and winning a protracted counter-insurgency war against well-armed and highly trained militia groups thousands of miles away in the Middle East. The figure leading the operation, General David H. Petraeus, is a true hero -- a remarkable military commander who defied the odds to deliver results in the face of a brutal, sophisticated and multifaceted enemy.

The improved security has brought with it a renewed sense of economic confidence and stability. Iraq today has more than 40,000 registered businesses, a 500 percent increase since the dark days of Saddam Hussein's rule. Crude oil production now exceeds pre-war levels, at 2.2 million barrels a day, and economic growth is expected to rise to 7 percent in 2008 and 8 percent in 2009.

Al-Qaeda remains though a potent threat in Iraq, and there can be no room for complacency. There is still much work to be done in securing the country, and the Coalition must stand united in ensuring that the gains of the past year are not reversed. As Petraeus warned in an interview with Human Events last week, "we should expect al-Qaeda to try to rebound. Al-Qaeda's like a fighter that's been dropped to the canvas a couple of times, but comes back off that canvas."

Despite a huge reduction in terror attacks across Iraq as a whole, sporadic bombings continue in parts of the country. The brutal killing of over 70 Iraqis in two Baghdad markets by al-Qaeda at the beginning of February, using two mentally disabled women as bombers, provided a stark reminder of the pure evil that Islamist militants are willing to unleash on the streets of Iraq. We should be under no illusions that, if given the opportunity, al-Qaeda will seek to emulate this kind of barbaric atrocity in cities across Europe and the United States.

These and other bombings in recent weeks have underscored the precarious nature of the progress that has been made in Iraq, and it is imperative that the West makes a long-term military commitment to defeating the al-Qaeda threat. Talk in Washington of a large-scale withdrawal of U.S. forces from Iraq after the end of the Bush Administration sends completely the wrong signal at a time of continuing uncertainty, and will only serve to embolden our enemies. An early withdrawal of American and other Allied troops would not only hand a huge propaganda victory to al-Qaeda, giving them tremendous momentum and reversing the progress of the past year, but it would also open the door for mass ethnic cleansing that would claim hundreds of thousands of lives.

The dangerous regime in Tehran also remains a major threat to long-term peace and stability in Iraq. Iran's Revolutionary Guard continues to arm Shia militia groups responsible for the killing of numerous British and American soldiers. It is vital that America's closest ally, Great Britain, maintains a significant military presence to act as a bulwark against Iranian aggression in the south. As significant progress is made in central Iraq, this is no time for Prime Minister Gordon Brown to go wobbly.

No great power can succeed entirely on her own, and the United States needs Britain to stand beside her. The Anglo-American alliance is the engine of the global war against Osama bin Laden and his murderous cohorts. The U.S. and UK are great warrior nations that have done more to advance the cause of liberty than anyone. The two have liberated over 50 million people from tyranny in Iraq and Afghanistan, a monumental achievement of which we should be proud.

Washington and London must ensure that Tehran does not gain a long-term foothold in Iraq's second biggest city, Basra. In the coming months, thousands of U.S. troops may need to be deployed to the region in a show of strength to warn Iran of the consequences of playing with fire. Over 4,000 Coalition troops have laid down their lives in Iraq since 2003, and it is important that their sacrifice be honored with a commitment to ensuring that an Iranian-backed Islamic tyranny does not take hold.

Ultimately, Iraq is a microcosm of a larger war the West is waging against Islamist terrorism and extremism. The battles on the streets of Iraq have a direct relevance to the national security of the United States and its allies, and to walk away from this frontline of the war against Islamist terrorism would significantly increase the terror threat to the West itself. It is a long-term conflict that must be fought to ensure the security of the free world. America's recent success in Iraq demonstrates that this is a war that can and must be won.