As for an Afghan quagmire...

...another view of the primaeval--in current "thinking"--one (via Spotlight on Military News and International Affairs):

The Real Afghan Lessons From Vietnam
The 'clear and hold' strategy of Gen. Creighton Abrams was working in South Vietnam. Then Congress pulled the plug on funding.
...
In the later years, Abrams ["Gen. Creighton Abrams took command soon after the 1968 Tet Offensive"], along with Ellsworth Bunker (at the head of the embassy in Saigon) and William E. Colby (in charge of support for pacification) devised a more viable approach for conducting the war even as U.S. forces were being incrementally withdrawn.

Security for the South Vietnamese became the new measure of merit. Instead of "search and destroy," tactical operations were now focused on a "clear and hold" objective. Greatly increased South Vietnamese territorial forces, better trained and equipped and integrated into the regular army, provided the "hold."

Abrams, Bunker and Colby regarded South Vietnam's President Nguyen Van Thieu as his country's "No. 1 pacification officer." Against the advice of virtually all his advisers, Thieu took the courageous step of organizing and arming a People's Self-Defense Force to back up localized defense forces that defended their home provinces. Thieu's own view, validated by the results, was that "the government had to rest upon the support of the people, and it had little validity if it did not dare to arm them." Ultimately four million villagers were enrolled in the self-defense force.

Thieu also implemented a "Land to the Tiller" program which, for the first time, brought real land reform to the South Vietnamese peasantry. By 1972 over 400,000 farmers had acquired title to two and a half million acres of land. Tenancy was eliminated.

Better intelligence and a structured Phoenix program (as the campaign against the enemy infrastructure was called) progressively identified and neutralized the enemy's covert infrastructure. Most were either captured or induced to rally to the government side, providing valuable sources of intelligence for going after the rest.

By the time of the enemy's 1972 Easter Offensive virtually all U.S. ground troops had been withdrawn. Supported by American airpower and naval gunfire, South Vietnam's armed forces gallantly turned back an invasion from the North amounting to the equivalent of some 20 divisions, or about 200,000 troops.

Critics were quick to attribute the successful defense to American airpower. Abrams would have none of it. "The Vietnamese had to stand and fight," he said. If they hadn't done that, "ten times the [air] power we've got wouldn't have stopped them."

When the last U.S. forces departed South Vietnam in March 1973 pursuant to the Paris Peace Accords, South Vietnam had a viable government and military structure that was positioned—had the U.S. kept its commitments—to sustain itself against the renewed aggression from the North that began almost immediately after the peace accords were signed. When America defaulted on those commitments, South Vietnam was doomed.

Lessons learned from the past are only as good as our understanding of the past. This is especially important to keep in mind now, as the commander in chief, his principal national security advisers, and senior military leaders contemplate the next step in Afghanistan. Analogies to the real history of Vietnam could be as useful as those based on a flawed understanding of that conflict are dangerous and misleading.

Mr. Sorley, a military historian and retired Army Lieutenant Colonel, is the author of "A Better War: The Unexamined Victories and Final Tragedy of America's Last Years in Vietnam" (Harcourt, 1999).

And note there's no Taliban regular army with armour and artillery. Nor likely to be unless they take over Pakistan (or at least get the equipment--not that much of it yet--from defeated, defecting and demoralized units of the ANA if the international military support goes poof).

Update thought: Though, as BruceR. has suggested, the Taliban may be in no need of armour and/or artillery against just the ANA.