Exactly twenty years ago, the last Soviet units left Afghanistan after a nine-year intervention that took 15,000 soldiers’ lives. As they crossed the Oxus, I was in the air above them, the only foreign journalist to fly to Kabul that day.

Russian friends in Moscow, where I was the Guardian’s correspondent, doubted my sanity, convinced a bloodbath was bound to follow the Soviet exodus. I disagreed. The secular regime under Mohammed Najibullah that the Kremlin left behind had a firmer base than many outsiders realised, thanks in part to support from Kabulis who feared chaos and blood-letting if the mujahideen won the civil war.

Two decades later the ironies of America’s war in Afghanistan are telling. When Richard Holbrooke, the new US envoy to the region, visited the country this week he may not have been aware of the Soviet anniversary. But the US-led intervention is already almost as long. At this stage of their war, the Russians were preparing to leave. Now the US and Nato want to get further in, and if Barack Obama’s plans for 30,000 extra US troops are met, along with efforts to get more from Nato, coalition forces will almost equal the 115,000 troops the Russians had at their peak.

Western casualties are considerably less, but Nato has been more successful. Like the Russians, the western alliance mainly occupies Kabul and provincial capitals. The countryside is vulnerable to attack or in the hands of the resistance – a mixture of Islamic fundamentalists, Pashtun nationalists, local tribal chiefs and mullahs, and Arab jihadis – just like the mujahideen who confronted the Russians. The difference is that the west and Pakistan supported and armed them in the 1980s. Now, using the profits of heroin-running, they are self-sustaining and harder to control.

Nato faces tougher challenges than the Russians. Twenty years ago the Taliban did not exist, suicide bombing was not in vogue, and the Afghan army and police were more effective. Kabul under Soviet rule was an oasis of calm, where girls went to school and unveiled young women attended university. The mujahideen fired occasional rockets into the city but caused too little damage to upset normal life. Note the contrast with today’s siren-screaming armoured convoys and western offices hidden behind high walls and sandbags, and still the Taliban were able to attack three government buildings a few days ago.

The Soviet invasion violated international law and was condemned by the UN. But its goals were more modest than the US’s in 2001. Moscow was not seeking regime change. It was trying to prop up a regime under threat from a mounting civil war. Although western hawks claimed the Kremlin planned to advance through Afghanistan to seize warm water ports in the Gulf, the true aim was limited. Moscow wanted to defend an allied government, contain the mujahideen (who were getting CIA support before Soviet troops invaded), and prevent Afghanistan becoming a pro-western bastion. This was shortly after the US was expelled from Iran and the Kremlin feared Washington wanted Afghanistan as its replacement.

Getting out was easier for Moscow than it will be for the US. International negotiations in Geneva gave the Kremlin the face-saver of “parallelism”. The peace terms were that the Russians would leave when aid to the mujahideen ceased and an intra-Afghan dialogue was launched. This disguised any appearance of defeat. It even provided a good chance for the Afghan government to continue after Soviet troops withdrew. In fact, it lasted three more years.

The causes and consequences of the Soviet withdrawal and Najibullah’s eventual fall have led to some of the phoniest myths of the cold war. Claims that US-provided Stinger missiles forced the Russians to give up and that this humiliation provoked the Soviet Union’s collapse are nonsense. Moscow’s ally Najibullah fell four months after the USSR died, when the Kremlin’s new ruler, Boris Yeltsin, cut fuel supplies to the Afghan army and Abdul Rashid Dostum, the leading Uzbek commander, defected to the mujahideen. Until that moment, they had not captured and held a single city.

Another myth is that the west “walked away” after the Russians left. If only it had. Instead Washington and Pakistan broke the Geneva agreement by maintaining arms supplies to the mujahideen. They encouraged them to reject Najibullah’s repeated efforts at national reconciliation. The mujahideen wanted all-out victory, which they eventually got, only to squander it in an orgy of artillery shelling that left Kabul in ruins and produced the anger that paved the way for the Taliban. If western governments are now paying a high price in Afghanistan, they have brought the disaster on themselves.

The Taliban will not drive Nato out militarily. The notion that Afghans always defeat foreigners is wrong. The real lesson of the Soviet war is that in Afghanistan political and cultural disunity can slide into massive and prolonged violence. Foreigners intervene at their peril.

Nato is in a cleft stick and the idea that, unlike Iraq, Afghanistan is the “right war” is a self-deluding trap. A military “surge”, the favoured Obama policy, may produce short-term local advances but no sustainable improvement, and it will cost the US and Britain enormous sums. Pouring in aid will take too long to win hearts and minds, and if normal practice is followed, the money will mainly go to foreign consultants and corrupt officials. Talking to the Taliban makes sense under Najibullah-style national reconciliation. But the Taliban themselves are disunited, with a host of local leaders and generational divisions between “new” and “old” Taliban. Worse still, since the war spilt into Pakistan’s frontier regions, there are now Pakistani Taliban.

What of the better option, a phased Nato withdrawal? It will not produce benefits as clear or immediate as the US pull-out from Iraq. Most Iraqis never wanted the US in the first place. They know the destruction the invasion brought, have stepped back from sectarian war, and now have a government which has pressed Washington to set a timetable to leave. In Afghanistan the risks of a collapse of central rule and a long civil war are far greater.—Dawn/The Guardian News Service