WASHINGTON, Aug 16 (Reuters) - America"s longest war is nearing its end, with a loss to the enemy it defeated in Afghanistan nearly 20 years ago, shock that the government and military it supported collapsed so quickly and chaotic eleventh-hour evacuation operations. And now, the 20th anniversary of the Sept. 11 attacks on New York and Washington will be marked with the Taliban back in power. “This hasn’t been a 20-year war. It’s been one-year wars fought 20 times,” said a U.S. military official to convey the frustration with short-term thinking, multiple missteps and a lack of consistency over four administrations. Interviews with nearly a dozen current and former U.S. officials and experts highlighted the failures that crippled U.S. efforts to stabilize Afghanistan that saw Washington spend more than $1 trillion and more than 2,400 American service members and tens of thousands of Afghans die, many of them civilians. Two Republican and two Democratic administrations struggled to fight corruption and human rights abuses even while acquiescing to much of them as they sought to nurture democracy and rule of law, build a strong Afghan military and keep war-weary Americans engaged. They promoted a powerful central government in a country where for centuries the tribes enjoyed local autonomy. Their drug eradication programs further antagonized people in the Taliban"s rural strongholds who rely on opium poppy cultivation to survive. Intelligence shortcomings also weighed, including last week when U.S. President Joe Biden"s administration anticipated it would take a few months for the Taliban to enter Kabul. They took just a few days. There were some undeniable successes. The United States and its partners helped improve countless lives in one of the world"s poorest countries, advancing the rights of women and girls, supporting independent media, and building schools, hospitals and roads. All of that is now under threat. DISTRACTED BY IRAQ President George W. Bush declared a “war on terror” and toppled the Taliban government in Kabul who had hosted al Qaeda militants responsible for the 2001 hijacked plane attacks. The strategy worked. For a while. The Taliban were routed and al Qaeda sent fleeing. But former officials and experts said that instead of working to secure Afghanistan against a resurgence of the Taliban, the Bush administration diverted resources, personnel and time to invading Iraq on the erroneous claim that Saddam Hussein"s authoritarian government had illicit weapons of mass destruction programs. "The United States did become distracted by the war in Iraq for several years," said Lisa Curtis, a former CIA analyst and regional expert who served in the Bush and Trump presidencies and now is a senior fellow at the Center for a New American Security. “It was the right thing to do to overthrow the Taliban ... Unfortunately, shortly after we routed the Taliban, then more attention began going toward the war in Iraq,” Curtis said. Current and former officials say the Bush administration’s obsession with Iraq left its Afghanistan strategy adrift. “Were we actually trying to help build and reform this nation (Afghanistan) or are we just trying to get out?” said Jonathan Schroden, an expert at the CNA policy institute, who served as an adviser to U.S. Central Command. When President Barack Obama came into office in 2009, the mixed messaging continued. He was looking to reduce U.S. forces in Afghanistan but agreed to a surge in a bid to pressure the Taliban into peace talks. In a speech at West Point in November 2009, he said he would send an additional 30,000 troops, but added that “after 18 months, our troops will begin to come home." In seeking to placate his domestic audience, Obama effectively told the Taliban that they could wait out the United States. ENDEMIC CORRUPTION As a presidential nominee, Obama called Afghanistan the “good war,” contrasting it with the military disaster in Iraq. U.S. troop levels swelled to over 90,000 by 2010, as did the funding. In the desperate and constant need for a stable government, the United States worked with Afghans who had influence but were enmeshed in corruption and human rights abuses. Peter Galbraith, a former U.S. ambassador who served as deputy U.N. representative for Afghanistan, said U.S. counter-insurgency doctrine stressed the need for a “local partner.” That led the United States, the United Nations, and other countries to legitimize successive Afghan governments, effectively accepting pervasive corruption even as they promoted anti-corruption efforts. That policy, he said, is illustrated by the blessings Washington, other countries, and the United Nations conferred on the 2009, 2014 and 2019 presidential elections despite knowing of massive fraud and other irregularities. “We don"t have the tool kit to root out endemic corruption in societies,” a former senior government official told Reuters, on condition of anonymity. Corruption infected the Afghan military as well, for which the United States allocated $88 billion over two decades. For example, the United States never fully overcame the problem of "ghost soldiers," non-existent troops listed on rosters by crooked commanders who took their pay. So while the Afghan security forces have 300,000 troops on paper, the actual number is much lower. A 2016 report by a U.S. government watchdog found that in Helmand province alone, about 40 to 50 percent of the security forces did not exist. THE PAKISTAN ISSUE Current and former U.S. officials say that the Taliban would not have won had successive U.S. administrations acted to end the sanctuary and other support that Pakistan and its Inter-Services Intelligence (ISI) agency gave the insurgents. “Without Pakistan, the Taliban would simply be a nuisance,” said Christine Fair, a Georgetown University expert on the Pakistani military. “They would not be a competent fighting force.” Islamabad repeatedly has denied backing the Taliban as part of what experts say is a strategy to secure an allied government in Afghanistan to blunt India’s influence. WAR WEARY PUBLIC President Donald Trump came into office in 2017 pledging to end what he called “ridiculous endless wars.” In part, Trump’s calculus was that Americans simply did not care enough about Afghanistan to spend billions of dollars annually as American troops died. It led to a deal with the Taliban in February 2020 for a complete withdrawal of U.S. troops if the insurgents met certain conditions. The Afghan government was cut out of the talks. John Bolton, a veteran of the Bush and Trump presidencies, told Reuters that the agreement was Trump"s biggest blunder and that Biden should have re-evaluated it. Biden, however, proceeded with a complete withdrawal against the advice of U.S. military leaders and without sorting out a backlog of special visa applications from Afghans at risk because they worked for the U.S. government, leading to a chaotic evacuation operation. He had grown skeptical of the military effort in Afghanistan after a 2009 trip to Kabul that convinced him that the United States was trapped in an unwinnable war. A U.S. official told Reuters on condition of anonymity that internal polling showed that most Americans supported a withdrawal, making Biden comfortable in his decision. An Ipsos poll in April confirmed that a majority of Americans supported Biden. What remains unclear is how Americans will view Biden"s decision after TV images of U.S. military helicopters evacuating the U.S. embassy and Afghans swarming the airport, desperate to leave. Biden insisted Kabul would be no repeat of the infamous U.S. evacuation from Saigon in 1975. “There’s going to be no circumstance where you see people being lifted off the roof of an embassy of the United States in Afghanistan," Biden said in July. Reporting by Idrees Ali, Jonathan Landay and Steve Holland; Additional reporting by Jeff Mason, Arlene Eiras; Editing by Mary Milliken and Grant McCool Our Standards: The Thomson Reuters Trust Principles.