A massive effort by US and Nato forces including offensives in the insurgent heartland and targeted assassinations of rebel leaders has failed to dent Taliban numbers over the past year, according to the military and diplomats.
A Nato official said this week that the alliance estimated current number of insurgent fighters at up to 25,000, confirming figures provided earlier by several military officers and diplomats.
That number is the same as a year ago, before the arrival of an additional 40,000 US and allied troops, and before the alliance launched a massive campaign to restore government control in Helmand province and around the city of Kandahar in southern Afghanistan.
The US-led International Security Assistance Force (ISAF) has kept official figures of enemy strength under wraps throughout the nine-year war. But non-US military assessments have tracked the growth of the Taliban from about 500 armed fighters in 1993 to 25,000 in early 2010.
"These are rough estimates, because they're not just standing around to be counted," said the Nato official.
The Taliban is pitted against about 140,000 ISAF troops - two-thirds of them Americans - and over 200,000 members of the government's security forces.
This gives the Allies a numerical advantage of at least 12-1 - one of the highest such ratios in modern guerrilla wars. At the height of the Vietnam War, the US and its allies had an advantage of between 4-5 to 1 over their communist foes.
President Barack Obama has doubled US troop numbers since taking office two years ago, hoping to inflict major losses on the Taliban before a planned pull-out starting this year. The intensity of combat has sharply escalated as a result, with both civilian and military casualties hitting record highs.
Despite the Taliban's ability to make up for battlefield losses, US and Nato commanders now insist they are making real progress throughout the country. They say hundreds of Taliban have been killed and others forced to abandon the movement's strongholds in southern and eastern provinces.
Meanwhile, the training of a 300,000-strong government security force is said to be going according to the plan adopted at Nato's summit in November. It calls for a gradual handover to Afghan troops and initial withdrawals of foreign forces by the middle of this year, concluding in 2014, when security throughout the nation will be transferred entirely to government forces.