The chaotic withdrawal of U.S. forces from Afghanistan was 20 years in the making, a key congressionally mandated watchdog agency concluded just days before the government’s collapse to the Taliban on Sunday.

The nearly $1 trillion in spending by the U.S. since late 2001 was hobbled by a shifting American strategy, Afghan corruption, unsustainable projects and a failure “to understand the Afghan context” after decades of war, according to a report Tuesday by John Sopko, the Special Inspector General for Afghanistan Reconstruction, or Sigar.

“If the goal was to rebuild and leave behind a country that can sustain itself and pose little threat to U.S. national security interests, the overall picture is bleak,” Sopko wrote in the report, drafted before the rapid Taliban takeover of the past week.

Thirteen years of Sigar reports issued warnings about inaccurate data inflating the size of Afghan forces. In one province, Sigar wrote, up to 70 percent of the reported security forces were “ghost soldiers,” or fictitious.

On Tuesday, it released the report highlighting the poor understanding America had of Afghanistan from the very beginning. The U.S. repeatedly failed to recognize the importance of ethnic dynamics within the security forces, for example.

“By providing material support and equipment to certain units” within the security forces “without consideration for ethnic dynamics between units, the United States could be perceived as biased in favor of one ethnic group or faction at the expense of another.”

Billions of dollars of spending on reconstruction efforts were hobbled by the high turnover in American staff who administered projects but who usually spent a year or less in the country before moving on.

Since 2002, “the U.S. government continuously struggled to identify the right personnel, train them properly, keep them in the country long enough to become effective, and enable them to spend enough time with their replacement to hand over their work before departing,” Sopko wrote.

Most damning from a cost perspective was how money spent became a measure of success, regardless of whether it was well spent.

There was “enormous pressure to demonstrate progress to the Congress and the American and Afghan people distorted accountability systems into spin machines.” The result was that “there was little appetite for honest assessments of what worked and what did not.”

By spending money “faster than it could be accounted for, the U.S. government ultimately achieved the opposite of what it intended: it fueled corruption, delegitimized the Afghan government, and increased insecurity,” according to the report. “Perversely, because it was the easiest thing to monitor, the amount of money spent by a program often became the most important measure of success.”

In an address to the nation on Monday, President Biden said he stood by his decision to withdraw and criticized Afghan forces – who were trained by the U.S. for two decades — for not putting up more of a fight. Biden’s critics said the withdrawal should have been delayed, and that the U.S. should have planned better for it.

But the latest Sigar report, beyond criticizing both Biden and Trump, made clear that every administration since George W. Bush’s can share in the blame.

Afghanistan was a country broken by decades of conflict by the time U.S. special forces arrived in late 2001, intent on ousting a Taliban regime that housed al-Qaeda leader and Sept. 11 plotter Osama bin Laden.

Besides a shattered economy with a “destroyed” infrastructure and the worst social indicators in the world, “Afghans had no experience participating in elections, much less administering them,” Sigar said, citing a March 2002 World Bank report. The report continued:

“There was no independent media, and civil society was anemic. Life expectancy was 56 years, lower than 83 percent of countries at the time. The mortality rate for children under the age of five was in the bottom 15 percent of countries globally. Women and girls were officially banned from schools and the workforce. Only 21 percent of eligible children were enrolled in primary school.”

Sopko’s review, following 13 years of reports on the successes and failures of U.S. efforts in Afghanistan, was reinforced by 760 interviews with current and former policymakers, ambassadors, generals, military officers, development experts, and other practitioners.

The report gave Biden credit for recognizing that 20 years of changing or incoherent strategy and nearly limitless spending “had failed to bring the desired change and stood little chance of doing so.”

But Biden’s decision “regardless of Taliban advances or where prospects for peace stood” also left “uncertain whether even the modest gains of the last two decades will prove sustainable,” it said.

The deal the Trump administration sought with the Taliban was also flawed from the start. Because the Taliban “has been ascendant on the battlefield for more than a decade, it was poorly motivated to indulge peace talks” in Doha, Qatar, “beyond what was necessary to secure the release of more than 5,000 prisoners, ensure the removal of U.S. and UN sanctions, accrue international legitimacy, and claim credit for negotiating the departure of U.S. forces.”

“Notably, none of those objectives required compromise with the Afghan government,” Sopko wrote.

Still, amid the debris of what looked like a failed intervention, “there is no doubt, however, that the lives of millions of Afghans have been improved by U.S. government interventions,” Spoko wrote. By 2018, for example, “life expectancy had jumped from 56 to 65, a 16 percent increase” since 2001.

Between 2000 and 2019, the mortality rate of children under five “plummeted by more than 50 percent” and “between 2001 and 2019, Afghanistan’s human development index increased 45 percent. Between 2002 and 2019, Afghanistan’s GDP per capita nearly doubled, and overall GDP nearly tripled, even accounting for inflation,” though economic growth was closely tied to international aid.

While the conflict killed 2,443 U.S. troops and 1,144 allied troops, Afghans bore the greatest burden, according to Sopko’s report. At least 66,000 Afghan troops have been killed and more than 48,000 Afghan civilians have been killed with at least 75,000 injured since 2001 — “both likely significant underestimations,” he wrote.