Here ends the west’s grotesque delusion that it could use its military might to turn Afghanistan into a stable democracy, a shining path of moderate Islam. In the shadow of New York’s burning twin towers, I was one swept along on that “something must be done” tide, that drumbeat for a war to stop terror and liberate oppressed people. We have learned a bitter lesson. How deceptively easy was the 2001 victory, as Taliban fighters fled to melt back into their own population famously murmuring, “You have watches, we have time.” They have just turned back the clock on 20 wasted years. A year after that empty “victory”, I was in Afghanistan, seeking signs of cultural transformations and social progress. But it was already clear the west had neither the political will, financial generosity nor the attention span to match the windy rhetoric that breezed us there. Remember how high-flown that oratory was. “This is a moment to seize,” Tony Blair told the Labour party conference in October 2001. “The kaleidoscope has been shaken. The pieces are in flux. Soon they will settle again. Before they do, let us reorder the world around us … only the moral power of a world acting as a community can. By the strength of our common endeavour we achieve more together than we can alone.” It was a powerfully moving vision – but dangerously mistaken. I doubt anyone will talk again of “reordering the world around us”, except the jihadists. No more Onward Christian Soldiers. Here finally ends the American century (though worse may follow). According to the Blair doctrine – expressed in his 1999 Chicago speech, persuading Bill Clinton and Nato to escalate their attempts to stop the mass expulsions of Albanians from Kosovo – there was a moral obligation to intervene. Do the right thing where you can. But Afghanistan failed two of his doctrine’s criteria: action must be “prudently [undertaken]” and only if one is prepared to endure for the “long term”. The invasion and occupation of Afghanistan was not “prudent” and there was never enough political and financial investment to “endure”. The 20-year “forever war” seemed a long endurance to Joe Biden, a feeling that was strongly backed by American polls. But not even $1tn and 4,200 Americans’ lives were enough. What the US right’s late guru, Charles Krauthammer, once called his country’s “uniquely benign imperium”, together with other Nato contributors, left President Hamid Karzai’s first budget when I was there with just $460m for his population, then 22.6 million. This was closer to the budget of an English local authority than anything that could create a new Afghanistan. So forget “reordering” what the World Bank called the “most miserable state in the world”, blighted by its geography between belligerents and cursed by a war-torn history. How eager the west’s politicians were to be misled by smooth-talking, western-educated leaders in Kabul promising the impossible, to root out corruption and spread good administration, even as they handed the military to warlords and the cash for security forces vanished. That was the imprudence, the hubristic wishful thinking about the culture and society they thought outsiders could “reorder”. Invasion brought not just culture clash, but wealth collision. NGOs and foreigners swarming in sent rents soaring for the only decent housing left standing in Kabul; they were competing to do good, each country bringing its own women’s project. The indignant minister for public works, earning $35 a month, beckoned me over to look at foreign officials’ and NGO cars: “Stand by my window and you’ll see 200 white Land Cruisers pass by in an hour! Our money they spend.” One local aid worker summed up the rich-poor clash: “They expect Pringles wherever they go.” Any slender hope for Afghanistan was blown away in Iraq. A year after the invasion, not just the military, but NGOs and all the carpet-bagging hangers-on of war zones were already packing to move on. “Next year in Baghdad,” some journalists and old NGO hands were calling out cheerily, as US news networks decamped, the story having gone cold. “Don’t go,” Afghan leaders pleaded. The minister for women’s affairs, a returned law professor, warned me of the fragility of new women’s rights. “If you leave us, the fundamentalists will rise up again.” That fear was as strong on my next visit eight years later: the Afghan people saw that the west’s leaders wanted out – and so did the patient Taliban. The Taliban and their pathological loathing of women didn’t spring from nowhere – the patriarchal structure of Afghan society was clear. Women were still shrouded in burqas with vision-blocking grilles. Men were still treating these invisibles as irritating objects, shunting them out of the way on pavements. “Saving women” was the reason so many of us backed the invasion – and much did improve in their work and life, mostly for those who were educated. Nothing was more moving than watching hundreds of eager girls crammed on benches in a dusty tent reciting letters off a board in three-hour shifts. That’s something gained, no lesson lost, and its effects for those who benefited will last a lifetime. But what now? Two girls’ schools were bombed the week before I was first there and, earlier this year, 85 girls were blown up in a school. Still only a third of women can read. Listen now to the voices of female journalists gripped with terror, whatever Taliban officials tell the world this week. What’s to show for 20 years? Afghanistan entered 2021 with 18.4 million people in humanitarian need. Life expectancy has risen – but only at the same rate as before. GDP has barely risen compared with other low-income countries. But those World Bank figures don’t include its dominant export, opium. The area of land given over to its cultivation rose by 37% last year, says the UN. The unrelenting “war on drugs”, with US bombing of heroin laboratories, barely touched opium growers’ trade – Afghanistan is the source of 95% of opiates on European streets. This is how the Taliban and the warlords draw their financial strength. Here their power and the country’s endemic corruption could have been dealt a mortal blow by legalising that global trade. Ending the failed drugs prohibition, which exploits “county lines” kids in Britain and breeds corruption in poor countries, is a powerful measure the west could embrace. Along with an urgent duty to take in Afghan refugees, that’s one genuine “reordering” that we should make as a final bequest to the country. The other is to learn the bitter realpolitik lesson of the Blair doctrine: without the will and capacity, his idea of “moral power” invites disaster. Polly Toynbee is a Guardian columnist