Washington DC - As newly deployed American forces begin to arrive in Afghanistan on President Donald Trump's orders, a larger strategic question hangs over their purpose. 
Can the US win enough cooperation from Pakistan and key powers in the region to forge a political settlement between the Afghan government in Kabul and Taliban insurgents?
The answer for Trump and his top advisers appears to be "not yet" and, seven months into his four-year term, the president is reversing a campaign promise to withdraw from Afghanistan. 
Instead, US president is sending about 3,900 more troops to bolster some 11,000 US forces already there - and has put Pakistan on notice.
Trump announced the shift in US posture in a nationally televised Speech staged before a military audience at Ft Myer on August 21. Instead of adhering to a timeline for withdrawal, which former president Barack Obama had attempted, Trump's policy will be "conditions-based", which effectively commits the US to remain in Afghanistan for four more years.

Trump is giving the American military more latitude to use air power and special forces to support the Afghan army. 
What had been largely a train-and-advise mission since 2014 is now shifting towards a more lethal posture.
Secretary of Defense James Mattis signed deployment orders August 31 and will brief members of the US Congress on details this week. And the White House announced it would withhold $300m in security aid from Pakistan until the Trump administration is satisfied Pakistan is taking measures against the Taliban.
"When the president talked about getting tough on Pakistan, we have heard that before from US governments that have taken certain actions in the past to try to pressure Pakistan.
Michael Fuchs. a senior fellow at the Center for American Progress and a former deputy assistant secretary of state in the Obama administration.