It's known in milspeak as RC-East, the vast, rugged and mountainous east of Afghanistan, where battle-hardened insurgents vow to wait out U.S. military might and the final phase of the decade-long war in Afghanistan is likely to be decided.
With a dwindling force, a ticking clock and a patient enemy, it appears doubtful that President Barack Obama can hope for more than to hold on to the fragile security gains U.S.-led NATO forces have already made there.
Afghanistan may garner little more than episodic attention in U.S. media and the cares of American voters. But in Washington policy circles, a debate is reverberating over Regional Command-East, which encompasses 14 provinces and a long stretch of porous border with Pakistan.
Across Afghanistan, U.S. and NATO forces have been unable to deal a decisive blow to Taliban insurgents and allies like the Haqqani network, blamed for a series of bold attacks on American targets.
Yet even more formidable challenges face foreign troops in the east, along with an uncertain ally across the border in Pakistan.
Secretary of State Hillary Clinton landed on Thursday in Islamabad, where she and the heads of the CIA and the Joint Chiefs of Staff will deliver a tough warning to Pakistan to cut suspected ties with militant groups that have severely strained ties between the uneasy allies.
Military experts such as retired General David Barno, who commanded U.S. forces in Afghanistan from 2003 to 2005, expect commanders in the Afghan east will, by necessity, focus on trying to sustain the modest security gains that have been made rather than routing a sophisticated, well-resourced insurgency.
"The bigger question now is: are you simply managing a withdrawal or are you trying to achieve a larger military and military objective?" Barno asked.
The dilemma in the east mirrors that across Afghanistan, as the White House orders a brisk withdrawal of the 33,000 extra troops Obama deployed following his 2009 overhaul of U.S. policy for a long-neglected campaign.
With a budget crisis at home and a presidential election on the horizon, the White House is forging ahead with withdrawal plans despite quiet fears among military officials that their hard-won gains could be reversed or that Afghanistan could slide into civil war on their watch.
Major General Daniel Allyn, who took over as commander in RC-East in May, voices confidence he can accomplish a mission that aims to disrupt the pipeline of weapons and fighters from Pakistan with a force of 33,000 U.S. and NATO soldiers.
Allyn's tightly focused mission also includes nudging a green but growing Afghan security force into the lead.
Geography as Destiny
A decade into the war, the West is seeking to weaken a host of insurgents, who in eastern Afghanistan also includes the independent Hezb-i-Islami group, and push them toward embryonic peace talks with the Afghan government rather than achieving a decisive battlefield victory in this long guerrilla war.
New data from the NATO force indicates that insurgent attacks in RC-East dropped in August and September compared to the same months of 2010, but it's too early to say if the trend will stick in a region where security festered for years as commanders focused on the Taliban's southern domain.
Overall attacks in RC-East increased, for instance, by over 20 percent from January through September.
The terrain alone is a major challenge in the Afghan east, where isolated valleys and impassible tracks often require helicopters to transport soldiers and supplies and make each mission exponentially more dangerous.
Those challenges are only intensified by the nature of the insurgent threat, with the bulk of the violence blamed on the battle-savvy Haqqani fighters.
The group -- which U.S. officials says is based in western Pakistan and has ties to Pakistani intelligence -- is also accused of launching a September 13 assault on the U.S. Embassy in Kabul and a recent truck bombing in eastern Wardak province.
"The Haqqanis are more tactically sophisticated, better trained, and in certain cases more entrenched in population centers" than the core of the Taliban, said Jeff Dressler, a security expert who has written extensively about the group.
"Even though commanders are fighting a very different opponent, they don't have the same resources," Dressler said.
General John Allen, the overall commander of U.S. and NATO forces in Afghanistan, has suggested he may rejig the allocation of foreign troops, sending more combat soldiers to the east. But for now soldiers in this rugged region must operate on the assumption they have to make do with what they have.
"It's quite apparent that this is not a conditions-based withdrawal, and as a result the troops may not be there," said Anthony Cordesman, a veteran security expert in Washington.
"That may force us to leave the south too weak, and not go into the east as we would like. So exactly what is it we're trying to do in RC-East?" Cordesman asked.
If commanders in the east will not receive a major infusion of fresh troops, their second-best wish list might include additional helicopters and enhanced surveillance capability.
Allyn said such extra air power and intensified surveillance was now provided to him on an as-needed basis.
"Commanders will do what they can with what they've got -- you've got to prioritize," a former RC-East staff member said on condition of anonymity.
The success of what may be a frugal U.S. strategy in RC-East is predicated, as it is across Afghanistan, on continuing improvements to local security forces. In RC-East, that means the 68,000-strong force of Afghan police, soldiers, and border police must work quickly to get up to speed.
Whether that can happen fast enough, given the western commitment to hand over control for Afghanistan's security by the end of 2014, is an open question.
"We can't stay there forever," the former RC-East staff member said.
(Additional reporting by Emma Graham-Harrison in Kabul; Editing by Warren Strobel and Philip Barbara)