Consider, first, the fate of three previous invasions of Afghanistan by two great European powers, Britain and Soviet Union, since the nineteenth century. 

These invasions ended in defeat - for the Europeans.

The first British occupation of Kabul lasted for four years. When the British garrison retreated from Kabul in 1842, it was picked off by Ghilzai warriors as they trudged through the snow. Only one British officer, William Brydon, survived this harrowing retreat. This solitary survivor was memorialized in a haunting painting by Elizabeth Butler, titled, Remnants of an Army.

The British occupied Kabul a second time in 1878, withdrew a year later, leaving behind a British resident to keep an eye on the Afghans. They returned the same year, when their resident in Kabul was killed in an uprising. When the British withdrew in 1880, discretely, they did not insist on leaving behind a British resident.

Nearly a hundred years later, 30,000 Soviet troops, invading from the north, occupied Kabul in December 1979. In order to oppose the growing Afghan resistance, the Russians soon raised their troop strength to 100,000 but never controlled any areas beyond the limits of a few cities. With 15,000 deaths, and unable to sustain growing casualties, the Soviets retreated in February 1989.

Will the United States fare better than Britain or the Soviet Union?

In terms of logistics, British India and Soviet Union were better placed than the United States. Afghanistan was next-door neighbor to both. It is half a world away from the United States, which, as a result, depends on long rail and road transit through Pakistan to supply and resupply its troops. Moreover, the supply routes - from Karachi to Kabul - are vulnerable to attacks by the Taliban and their allies in Pakistan. 

Alternative land supply routes would have to pass through Russia or Iran. Russia might make these routes available, at a steep cost, and keep raising the cost as US troop concentration in Afghanistan rises. Dependence on the Russians may turn out to be trap. Almost certainly, the Iranians will refuse, since, to do so, would badly tarnish its image with Sunni Islam.

The Soviet and British invaders primarily had to deal with Afghan fighters. The Americans are fighting the Taliban on both sides of the Afghan border, who, besides the Pushtuns, also have help from several extremist groups based in Punjab and Pakistani Kashmir. 

Pakistan, America's indispensable ally in the war against the Taliban, is an unwilling partner at best; it is also unreliable. Pakistan army has been gang-pressed and bribed into fighting the Taliban, and, as a result, the war is not popular with the junior officers and soldiers. In a rising spiral, Pakistan's war against the Taliban has provoked them to carry their war deeper into Pakistan. At some point, this could split the Pakistan army, intensify Taliban attacks on Islamabad and Lahore, or force Islamist and nationalist officers to take over and end Pakistan's collaboration with the United States.

Under pressure, the Taliban could launch another attack inside India. After the attacks on Mumbai last November, India was threatening 'surgical strikes' against Pakistan, forcing Pakistan to divert its troops to the eastern front. Another Mumbai, followed by Indian surgical strikes against Pakistan, could produce consequences too horrendous to contemplate. 

Are US objectives in Afghanistan so vital as to bring two nuclear powers to the brink of a war?

Iran was not much of a factor when British India and Soviet Union were fighting in Afghanistan. It is now. In Iraq, Iran favored the defeat of the Sunni insurgency once it had denied the United States a victory. In Afghanistan, Iran prefers to create a quagmire for the Americans, ensuring a long stalemate between them and the Taliban.

In light of the consequences that have flowed from the US presence in Afghanistan, who would advise an escalation? President Obama still has time to put on hold his plans to send more troops to Afghanistan. Instead, the best political minds around the world should be examining the least costly exit from a war that promises to become a quagmire, at best, and, at worst, a disaster, which no US objective in the region can justify. 

Unless, dismantling the world's only Islamicate country with the bomb is an objective worthy of such horrendous costs.