As the Iraq war enters its sixth year, the majority of Americans are disillusioned with the conflict and want U.S. troops to begin to come home. The sad news from military experts, however, is that the war has only entered “middle age” and won’t end for another five years or more.

This is not the war that was sold to the American people. Every rationale for the war has evaporated – there were no weapons of mass destruction, there was no connection between Saddam Hussein and al-Qaida – yet the need for the presence of U.S. troops has not.

Despite intense debate, Congress last year failed to pass measures that would result in any meaningful change in tactics or troop numbers in Iraq. Unthinkable when the war began in 2003, managing the Iraq war and finding a feasible U.S. exit will be the job of the next president. And perhaps the one after that.

Iraqi officials estimate they can’t assume responsibility for internal security until 2012 and won’t be able to defend the country’s borders until 2018, Lt. Gen James Dubik, leader of the Multi-National Security Transition Command, recently told the House Armed Services Committee.

Military analysts say insurgencies last an average of 10 years after which recruitment and strength drop off. But some, such as the FARC fight in Colombia, have lasted for decades.

“Iraq is a fight that, no doubt, is evolving,” said Brian Fishman, a professor at West Point. “But when you talk about some kind of end for American troops, it’s certainly in terms of years.”

This is not what the American people expected when President Bush, decked out in a flight suit and standing aboard an aircraft carrier beneath a banner that proclaimed “Mission Accomplished” on May 1, 2003, said “major combat operations in Iraq have ended.”

If this is not the war we were told to expect, it is the war we have and must deal with.

According to the most recent ABC News/Washington Post poll, 63 percent of respondents feel that the Iraq war has not been worth the cost. Those costs have been monumental. Nearly 4,000 American soldiers have been killed and 30,000 wounded, thousands severely. A quarter or more of returning veterans, many of them National Guard members, are suffering post-traumatic stress disorder, depression and other consequences of the war.

Hundreds of thousands of Iraqis have likely been killed and as many displaced, robbing the country of its middle class businessmen and consumers, its civil servants, doctors and professors – its economic engine and its future.

The Iraqi government remains largely paralyzed by disagreements among the country’s ethnic and religious groups. In the streets, these disagreements are deadly with Shiite and Sunni militias fighting for territory and control. A full-scale civil war is still possible.

The war has also been costly financially, draining $500 billion from the U.S. Treasury, ten times more than the Bush administration said was necessary to fund the war. That money could have supported overstretched social service and medical programs in the United States.

After five years, the nagging question remains: what now? Congress has failed to muster support for a change in direction, despite Democratic campaign pledges in 2006 to “Withdraw Now.” Part of the reason for inaction is that there is no easy path forward. Immediate withdrawal sounds good, but if the situation in Iraq gets much worse as U.S. forces leave, should their departure continue? What obligation does the U.S. have to improve living conditions for the average Iraqi since our military actions are partially responsible for their despair? How long does that obligation last? How should the country’s obligation to Iraqis be weighed against its obligation to its own citizens?

These are difficult questions. Although the necessity to answer them was not apparent five years ago, they must be answered now.

Although the economy has now taken center stage in the presidential campaign, the duration and extent of U.S. involvement in Iraq remains a crucial issue. It is an area of stark contrast between the Republican nominee, John McCain, and the potential Democratic nominee, either Hillary Clinton or Barack Obama. Sen. McCain said U.S. forces should remain in Iraq as long as it takes for the U.S. to be victorious there, while both Sens. Clinton and Obama favor beginning a withdrawal upon taking office with Sen. Obama pledging to move quicker to remove all troops than Sen. Clinton.

The Iraq War has defined the Bush presidency, largely in a negative fashion. It will be up to a new president to craft a way out that does not leave the country worse off than it was in 2003.