It was on February 2009 US President Barak Obama additionally sent 17000 troops with the already existing US troops and NATO members. Obama replaced Gen. David McKiernan with Gen. Stanley McChrystal; McKiernan was shifting U.S. strategy in Afghanistan. McChrystal was appointed to bring new changes in the strategy.

First, they give importance to protecting people rather than killing militants and they also tried to persuade the opponent and reconciliation between the Karzai government and Taliban leaders. After Afghan policy review, the president delivered a speech at the U.S. Military Academy saying 30,000 additional troops being deployed to Afghanistan by the summer of 2010, but the new strategy led to an increase in U.S. combat passings, amid the primary three months of 2010, U.S. passings were twice that were in 2009.

Obama made his inaugural visit to Afghanistan on March 28, where he conveyed a stern message to Karzai, urging him to address the pervasive corruption within his administration. This call for action came in the wake of widespread accusations of electoral fraud surrounding Karzai's re-election for a five-year term in 2009. Karzai also tried to reconcile with the Taliban, but the Taliban leader steadfastly refused. This made US to pressure Karzai, were he lashes out and even threatened to join the Taliban if the international community did not stop meddling in Afghan affairs, but later Karzai and Obama tried to make an effort to mend their relationship.

In June 2010 there was a significant change when Obama replaced McChrystal with Gen. David Petraeus after McChrystal and some of his aides when they made a remark to a Rolling Stone magazine reporter about Obama and other top administration officials, including Vice Pres. Joe Biden, National Security Advisor James L. Jones, and special representative to Afghanistan Richard Holbrooke.

Petraeus, recognized as a primary figure in shaping U.S. military counterinsurgency strategy, advanced McChrystal's concept of safeguarding the Afghan populace against insurgents, establishing Afghan governmental structures, and striving to minimize harm to civilians. Soon McChrystal's dismissal there was leak of information by raw intelligence gathered between 2004 and 2009, relating number of casualties and other details, in this US criticized as security breach but reveal that it doesn't contain anything new.

In 2011 May, Bin Laden was killed by U.S. forces and on June Obama announced the withdrawal of U.S. forces from Afghanistan, saying that the United States had achieved its goals by disrupting al-Qaeda's operations and killing many of its leaders. Later France also began to withdraw its 4,000 soldiers from Afghanistan. In September, Burhanuddin Rabbani, a former Afghan president and a key figure in reconciliation negotiations, was assassinated by a suicide bomber.

In 2012 there increase a tension between US and Afghan when a video began to circulate US Marine urinate on the dead body of dead Afghan and also there was an internal attack against NATO while they were training the Afghan solider later suspending it.

In early 2012 in the month of March and April they agreement but the Afghan was not happy with this and again in the month of May they made a outlining to framework for economic and security cooperation between the two countries following the withdrawal of NATO combat troops in 2014.The issue of leaving troop after withdrawal of NATO remained unsolved.

In late September 2014 the Bilateral Security Agreement was signed by the President Ashraf Ghani, from there the U.S. and NATO formally ended their mission in Afghanistan on December 2014, but approximately 13,000 troops were retained to support and train Afghan troops until a complete withdrawal 2020. However, after the complete full withdrawal in 2021 the Taliban's resurgence amid the withdrawal led to a situation reminiscent of the conditions when U.S. forces first entered the country two decades prior.

Reference:

• https://www.britannica.com/event/Afghanistan-War/U-S-troop-surge-and-end-of-U-S-combat-mission
• https://www.cfr.org/timeline/us-war-afghanistan
• https://study.com/learn/lesson/us-invasion-afghanistan-causes-controversy-war.html