Even as recent progress in Iraq raises hopes of a reduction of US troops there, the other, often overlooked front in the war on terror is pointing in the opposite direction.
So far, President Bush has been cautious in his appraisals of how the death of Abu Musab al-Zarqawi and the long-delayed naming of three key Iraqi government ministers will affect "the situation on the ground" in Iraq. But politicians in both the United States and Iraq have pressed the issue, putting forth new troop-withdrawal timelines of their own.
At the same time, however, Afghanistan is offering a note of caution about the challenge of removing America's military might from a country still finding its feet. There, as US forces pull back from the volatile south in anticipation of the arrival of NATO troops, insurgents are taking advantage of the vacuum in the most violent year since the fall of the Taliban in late 2001.
Any transition from an occupying force to a new authority will invite some measure of violence as enemies test its will, experts say. But Afghanistan's experience offers lessons on when and how American forces should leave Iraq.
"Handoffs have got to be made [only when the new force] has the capacity of taking the handoff," says William Nash, a military analyst for the Council on Foreign Relations.
Iraq's politicians suggest that they are ready. The country's national security adviser recently suggested that coalition forces should drop to fewer than 100,000 by year's end and should be gone within two years.
In Congress, Sen. John Kerry (D) of Massachusetts submitted an amendment to the defense authorization bill this week to withdraw most US troops from Iraq by the end of this year. It has almost no chance of passing, but it signals renewed pressure to move toward an endgame.
Yet in recent months, Afghanistan has offered a more sober perspective. Long held up as America's success in the war on terror, Afghanistan is showing signs of added stress. Violence has increased every year since the US invasion of 2001, but this year the Taliban has been able to temporarily seize and occupy territory for the first time since their ouster.
Insurgents are, at least in part, exploiting the transition between US and NATO authority in the south. For their part, US and NATO commanders say they will be able to reverse the trend when NATO reaches full strength in the fall.
Others, however, say the resurgent violence points to a need for the US to provide more help for NATO. Even when NATO operations in southern Afghanistan are fully up and running, the alliance's strengths tend toward nationbuilding functions like training, experts say. To succeed, NATO will continue to need US forces for high-intensity tasks like counterinsurgency.
"My concern about Afghanistan is that we are taking a 'we versus they' attitude toward NATO," says Mr. Nash. The message, he adds, is that Afghanistan is "their problem."
American forces have sought to dispel that notion. Wednesday marked the start of the largest US-led offensive since the 2001 invasion. More than 11,000 American, British, Canadian, and Afghan troops aim to roust insurgents from their strongholds in the south.
It is likely that similar cooperation will be needed far into the future in Iraq, as well. "[Iraqi forces] are not going to have artillery and helicopters" either, says Nash.
Perhaps the greater concern laid bare in Afghanistan is the danger of leaving a government unable to exert its authority. Mr. Bush pointed to this after he met Tuesday with Iraq's prime minister in Baghdad.
Iraqi leaders "were deeply concerned that the stability provided by coalition forces will be removed, and there'll be a vacuum," Mr. Bush told reporters. Wednesday, in a Rose Garden news conference, he pledged to keep enough US forces in Iraq "for the government [there] to succeed" and declined to offer a timetable for drawing down troop levels.
In Afghanistan, insurgents have entered that vacuum. "If you have a weak government, you're going to have support for the insurgency," says Seth Jones, a terrorism expert at the Rand Corp. "Why should these people support the government against insurgents so long as that government is viewed as incompetent?"
Even the US commander in Afghanistan agreed that the violence there stems from lack of government authority in southern Afghanistan. "It's not necessarily the strong enemy, it's the very weak institutions of the state," said Army Lt. Gen. Karl Eikenberry in a May briefing.
The same trend is at work in Iraq now, where militias have filled the spaces vacated by a weak government. Part of the solution lies in improving the performance of the police. "As the insurgency ramped up in Afghanistan, the police have largely been a failure," says Dr. Jones.
But the deeper issue is taking on the militias themselves – destroying, co-opting, or disbanding them. "At some point, we're going to have to deal with them," says Jones, "or else you are going to end up with a weak government."