WASHINGTON -- Donald Trump and Hillary Clinton have said next to nothing about how they would handle the war in Afghanistan.

That's remarkable, given the enormous U.S. investment in blood and treasure over the past 15 years -- including two American deaths on Thursday -- the resilience of the Taliban insurgency and the risk of an Afghan government collapse that would risk empowering extremists and could force the next president's hands.

In addition to the two service members killed on Thursday, four others were wounded while assisting Afghan forces in the northern city of Kunduz.

President Barack Obama escalated the war shortly after he took office, but he fell short of his goal of compelling a political settlement between the Taliban and the Afghan government. The next president will face a new set of tough choices on Afghanistan early in his or her term, including whether to increase or reduce U.S. troop levels and, more broadly, whether to continue what might be called Obama's minimalist military strategy.

The difficulty of these choices may explain, at least in part, why Trump and Clinton have been largely silent on Afghanistan. They ignore it while campaigning; it came up only in passing during the first Trump-Clinton debate and was not mentioned at all during second and third debates.

OBAMA'S FAILED MISSION

If Obama's eight-year struggle is a guide, his successor will not have an easy time disentangling the U.S. military from Afghanistan. Nor is there an obvious way in which a bigger U.S. military role could end the war.

Neither Trump nor Clinton has offered more than broad clues about their intentions toward Afghanistan. Trump has called for an end to U.S. "nation-building" efforts. Clinton has said she would "deal with" the Islamic State affiliate in Afghanistan and "stem the flow of jihadists" to and from Afghanistan. Neither of the candidates' websites, which usually go into detail on policy matters, have a mention of the U.S. military presence in Afghanistan or what to do about it.

Shortly after entering the White House in 2009, Obama undertook a lengthy review of U.S. policy on Afghanistan and Pakistan with the eye toward fixing what he saw as U.S. failures there. He pushed U.S. troop levels in Afghanistan to 100,000, but the surge did not force the Taliban to the negotiating table. The war dragged on.

Obama ended the U.S. combat role in December 2014 and said that by January 2017 the military would be reduced to only a "normal embassy presence." But in October 2015 he put the skids on a full withdrawal, saying 5,500 troops would stay to support Afghan forces and to continue counterterrorism operations against al-Qaida. In July, with about 10,000 U.S. troops still there, he scrapped the 5,500 target. He pledged to keep 8,400 troops through the end of his term to continue training and advising Afghan forces and to maintain a counterterrorism mission.

AFGHANISTAN 'AT RISK'

Washington has praised Afghan President Ashraf Ghani as a more effective U.S. partner than his predecessor, Hamid Karzai. But the political dimensions of Afghanistan's problems are in some ways as worrisome as those on the military and security side.

The so-called unity government set up in 2014 is led by Ghani and Chief Executive Abdullah Abdullah, who have been bickering since they took office. The rift has threatened to send the country further into chaos. Afghans are increasingly convinced the double-headed government cannot endure.

National Intelligence Director James Clapper earlier this year told Congress that Afghanistan is "at serious risk of a political breakdown in 2016." On the other hand, Afghan officials say the country's progress since 2001 is often overlooked or underestimated. Hamdullah Mohib, the Afghan ambassador to Washington, in September ticked off several examples: More women are serving in government positions than at any time in Afghan history, anti-corruption measures have produced a 22 per cent increase in national revenue and more rural families have access to electricity.

NO END IN SIGHT

One measure of the intractable nature of the war is the language American officials have used to describe it. As far back as February 2009 the top American commander in Afghanistan said the U.S. and its Afghan partners were "at best, stalemated" against the Taliban. Seven years later, in September 2016, Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, told a congressional committee the war was "roughly a stalemate."

Just a few days after Dunford's comments, the current commander in Afghanistan, Gen. John Nicholson, said the government and the Taliban had "reached some sort of equilibrium" on the battlefield. "This is a positive," Nicholson said, in the sense that the government controls nearly 70 per cent of the population. One might also say it's a negative in the sense that nearly one-third of the population is NOT under government control, even after years of fighting a Taliban group that in December 2001 was seemingly defeated.

There is no consensus view on how much longer the U.S. would need to keep troops there to help Afghan forces avoid defeat.

The inattention to Afghanistan during the presidential campaign is seen by Stephen Walt, professor of international affairs at Harvard university, as symptomatic of Americans' "war amnesia." Writing for the Foreign Policy website, Walt called Afghanistan a conflict "we seem readier to forget than to end."