The withdrawal of international forces from Afghanistan in 2014 has led to a significant increase in militant activity across the Central Asian country - most notably from a resurgent Taliban, which has gained hold of nearly half the country.

The "Islamic State" (IS) militant group has also created a small but significant presence, although its leader, Abdul Hasib, was killed last month in a US-led special forces operation.

With attacks on the rise, US President Donald Trump's top military advisers have called for an increased role in Afghanistan through the deployment of additional troops.

"We have a shortfall of a few thousand," NATO Resolute Support Commander John W. Nicholson told a congressional committee in February during a hearing on the state of the US's longest war in history.

The fight "is going to be far-flung," US Defense Secretary James Mattis said during an unannounced trip to Afghanistan in April. Though Mattis did not provide details on the Trump administration's next maneuvers, he said an increase in troops had not been ruled out given the current "stalemate" with the Taliban.

"Right now, we're engaged in defining the challenge," Mattis said. "There's no one nation that's going to carry all this," he added, referring to Trump's directive to assess the situation in Afghanistan and compile options on how to move forward.

'Hard and quick'

As analysts have called for a policy shift in Washington, the Trump administration has prepared the announcement of its strategy in Afghanistan, to be released "very, very shortly," Mattis said on Monday.

Trump is expected to deliver his policy vision for Afghanistan ahead of a NATO leaders meeting that the he plans to attend this month. But, given Trump's knack for contradicting his advisers, it is unclear which path he will choose to move forward with on Afghanistan.

In 2013 Trump had called for the removal of all US troops from Afghanistan, tweeting: "No more wasted lives. If we have to go back in, we go in hard and quick."

As president, however, Trump has sanctioned increased aerial and ground attacks in Afghanistan, including dropping the US's largest conventional bomb, commonly referred to as the "mother of all bombs," on IS targets in April.

The Taliban's comeback

In 2016, nearly 7,000 Afghan soldiers were killed and more than 11,000 of them wounded in assaults, many of them carried out by the Taliban. The attacks also led to the deaths of 8,400 civilians, according to a report published in January by the US's Special Inspector General for Afghanistan Reconstruction.

In April, up to 140 members of the Afghan army were killed in an attack on a military compound claimed by the Taliban in the northern Balkh province, marking one of the worst such incidents since 2001.

Though IS has etched a presence in Afghanistan, a resurgent Taliban has proved to be the formidable force that the United States still must overcome to meet its goals.

Under the Trump administration, Washington has voiced an apparent openness to peace talks with the Taliban after regional efforts failed to jump-start a reconciliation process. But US officials, including Mattis, have stipulated that the militant group must "renounce violence and reject terrorism" before entering a peace process.

NATO's advice

NATO has defined its role through its Resolute Support operation, which serves as an advisory mission to Afghan forces. Roughly 13,500 NATO troops are currently deployed for that.

Though the US has the largest number of troops in the mission, Germany ranks third, with 980 soldiers deployed to Afghanistan under NATO's banner. Given Trump's pressure on allies to bolster defense spending across the alliance, his administration may seek to increase NATO's role if he opts for a proactive policy on Afghanistan.

Nicole Birtsch, Afghanistan researcher at the Berlin-based German Institute for International and Security Affairs (SWP), told DW that Chancellor Angela Merkel has reaffirmed the importance of the Bundeswehr to the NATO operation, and said the prospect of increasing its role should not be ruled out.

"Germany follows NATO's policy of supporting Afghanistan as long as it is necessary and emphasizes the importance of an Afghan-led political solution," Birtsch said.

An argument for this kind of involvement is that it "could be an important step to increase troops to reinforce the Afghan forces in their fight against 'IS' and the Taliban, with the aim to provide the Afghans more time and leverage to push the Taliban peace talks," she added.

'Two sides of the same coin'

If Trump's advisers get their way, Washington will likely increase the number of troops serving in Afghanistan by a "few thousand," as echoed in Resolute Support Commander Nicholson's testimony to Congress. But deploying more soldiers would not mean the end of a war that has raged since 2001. 

"An increase of 3,000 to 5,000 troops may lead to some tactical gains, but military support and training will not be sufficient without political solutions," Birtsch said.

"The strength of the Taliban and the vulnerability of the Afghan security forces are two sides of the same coin," she added. "They draw on unresolved grievances, power struggles between ethnic and regional groups, and a government that is not able or willing to deliver to its citizens."

In real terms, bringing the Taliban to the negotiating table and establishing a political solution will require more than military hardware and troops. It will, according to the US's Special Inspector General for Afghanistan Reconstruction, require a holistic vision for rooting out corruption, establishing good governance and supporting reconstruction and development. Whether that is the foundation of Trump's policy remains to be seen.