WASHINGTON — The watchdog responsible for monitoring the U.S. government’s effort to rebuild Afghanistan says the 15-year, $5 billion effort hasn’t worked, according to a report released Thursday.

The Special Inspector General for Afghanistan Reconstruction (SIGAR) says the U.S. set unrealistic expectations for stabilizing Afghanistan on a short timeline, that the Obama administration lacked the political will to invest the necessary time and effort to stabilize the country, and that some efforts to bolster the Afghan government actually backfired.

“[Our] overall assessment is that despite some heroic efforts to stabilize insecure and contested areas in Afghanistan between 2002 and 2017, the program mostly failed,” said John Sopko, head of SIGAR, at a Thursday morning event announcing the report.

The report examines stabilization efforts from 2002, soon after the U.S. began military operations in the country, to 2017.

In 2003, the U.S. launched a counterinsurgency mission in Afghanistan that would come to include a clear-hold-build strategy. U.S. forces were instructed to clear an area, hold it and then build institutions.

The report says the effort proved ineffective in stabilization because the military focused on the most dangerous districts first, where poor security made it hard to move on to the building phase. U.S. civilian agencies were compelled to conduct their stabilization programs in dangerous areas not ready for rebuilding, and once coalition troops and civilians left those districts the stabilization ended.

Some efforts to introduce increased Afghan government control also produced unintended consequences, according to the report, because they created more opportunities for corruption.

By 2008, the security situation in much of the country had deteriorated and insurgent attacks began to mount.

The report focuses most of its attention on a period beginning in 2009, when the incoming Obama administration attempted to reverse the decline, and when the U.S. spent the bulk of the $4.7 billion that has been dedicated to stabilization since 2002.

But the Obama administration also had a drawdown clock for removing U.S. forces from Afghanistan, and the report says the decision to draw down forces on timelines unrelated to conditions on the ground “had a profound and harmful impact” on later decisions about stabilization.

Afghan President Ashraf Ghani, left, inspects an honor guard at the presidential palace in Kabul, Afghanistan on Sept. 29, 2016. Rahmat Gul / AP file

According to the report, the U.S. military and State Department were continually racing against this clock, which said that in 2011 U.S. “surge” troops would start to leave the country, and in 2014 the Afghan government would take security control of the entire country.

In 2009 and 2010, the Obama administration committed more than 50,000 troops to clear the most dangerous areas of the country, and hundreds of civilians followed to rebuild the war-torn areas. The surge was limited to 18 months.

“In the hope of compensating for a lack of time,” the report says, the U.S. threw more money at the problem, increasing spending in the most dangerous areas. The large sums of money spent “in search of quick gains often exacerbated conflicts, enabled corruption and bolstered support for insurgents.”

Without consistent security progress in any district, locals were not convinced the coalition could protect them if they turned against the insurgents, according to the report. And without confidence in the government, they were too afraid to serve in the local government and military.

Afghan President Ashraf Ghani, center, former President Hamid Karzai, right, and Chief Executive Abdullah Abdullah, left, at the presidential palace in Kabul, Afghanistan on Sept. 29, 2016. Rahmat Gul / AP

One solution was to build the Afghan Local Police (ALP) to compensate, but it grew at what the report terms an “unsustainable rate” from 6,500 in 2011 to 24,000 in 2013. Militias that had operated outside the government were absorbed into the ALP without proper vetting.

In general, the report finds that the U.S. government “greatly overestimated its ability to build and reform” Afghan government institutions and did not tailor the programs to Afghanistan.

“Even under the best circumstances, stabilization takes time. Without the patience and political will for a planned and prolonged effort, large-scale stabilization missions are likely to fail.”

Despite the harsh assessment, SIGAR writes that future efforts to stabilize other nations should not be abandoned.

“Poor results of this particular stabilization mission make it tempting to conclude that stabilization should not be conducted in the future at all,” says the report. Future efforts could be successful, the report concludes, if there are realistic expectations of the level of effort required and what is achievable, better preparation and improved oversight.