Ten years ago, al-Qa'ida terrorists struck New York, killing nearly 2700, including 11 Australians. Just over a year later, radical Islamists bombed a disco in Bali, killing just over 200, almost half of whom were Australian.

As memory of those tragedies fade, many Australians question their participation in the war on terror. Whereas three years ago, the Australian mission in Afghanistan was relatively popular, polls now show almost two-thirds of Australians want their troops withdrawn from Afghanistan.

The Indonesian government's execution of the Bali bombers in November 2008 and the dispatch of Osama bin Laden in May provide natural closure, they argue.

"To win the war on terrorism, the West must deny extremists the safe havens from which they will attack the West." -- Michael Rubin

Julia Gillard and Tony Abbott, however, are correct to hold firm in the face of public opinion. They recognise that the ideology that guides al-Qa'ida and other Islamist radicals targets Australians not because of Australian troops abroad, but because Australia embraces Western liberalism.

Some scholars downplay the ideological nature of terrorism and instead argue that terrorism is grievance-based. End foreign military presence in Islamic lands or impose Palestinian statehood and terrorism will disappear.

This, of course, is nonsense. Years before the land disputes that arose from India and Palestine's partition, the Muslim Brotherhood in Egypt was assassinating politicians it considered insufficiently Islamist. Anti-Western terrorism today is driven by Saudi Arabia's and revolutionary Iran's export of their radical interpretations of Islam. The ideology that motivates Islamist terrorism poses as great a threat today as a decade ago.

The problem lies in a strain of theology that developed against the backdrop of Saudi Arabia's oil boom. As Saudis strove to acquire televisions, Cadillacs, and lipstick, local religious scholars began to preach that these goods represented a plot by the West to pry young Muslims away from religion. Western pundits and professors today may argue that jihad, when violent, can be only defensive because the West fired the first shot with a deliberate cultural assault. For those who embrace this paranoid and xenophobic notion, Neighbours is as threatening to Islam as a stealth bomber over Mecca. These Islamists believe that Australia, the US, and Europe are on the offensive because Western norms and liberal values are a casus belli.

While it is fashionable to view wars in Iraq and Afghanistan as the drivers of terrorism, facts suggest otherwise. Before 9/11, president Bill Clinton prioritised diplomacy over military strategies. Clinton refused to retaliate after the 1993 World Trade Centre attack, bin Laden's 1996 declaration of war on America, and the USS Cole attack to avoid a cycle of violence. But American passivity did not convince al-Qa'ida to cease targeting Americans first in East Africa, and then in the US itself.

Bin Laden's death may be a major triumph, but he long ago ceased being more than the symbolic leader of global terrorism. Because bin Laden was effectively off the grid, jihadists debated how to operate. Some such as Abu Musab al-Suri emphasised the need for a decentralised structure to defeat surveillance and counter-terror teams. Accordingly, al-Qa'ida has spawned franchises operating in Yemen, Iraq, Somalia, and the Sahara, as well as affiliates in Pakistan.

Others such as Abu Bakr Naji emphasised the need to possess territory. Today, al-Qa'ida has free rein in its Somali, Saharan, Yemeni and Pakistani safe havens. Failure to deal with these safe havens would replicate the counter-terrorism mistakes of the 1990s. The worst thing Western leaders can do in the wake of bin Laden's death is to cut a deal with the Taliban, declare victory and come home.

Territorial concessions backfire. In 2009, the Pakistan government cut a deal with Islamist militants, ceding control of a mountainous district to the local Taliban. The Taliban used their new safe haven as a base from which to regroup and in three months was marching on a district just 100km from Islamabad.

To win the war on terrorism, the West must deny extremists the safe havens from which they will attack the West. After Western forces withdrew from Nuristan and Kunar in Afghanistan, the militants filled the vacuum.

If Australia leaves Oruzgan, the same pattern will occur. If Australia, Europe or the US walk away from the fight, al-Qa'ida will simply find fewer obstacles to overcome as they plot attacks against Australians or Americans, or seek to destabilise moderate Muslim countries such as Indonesia and Malaysia.

A premature withdrawal of troops would simply snatch defeat from the jaws of victory.

Michael Rubin is a resident scholar at AEI.