In both of America's bloodiest wars after 1945--the Korean War and the Vietnam War--U.S. allies tried to sabotage a peace deal parlayed by Washington.

The U.S. spent the last two years of the Korean War, from 1951-1953, negotiating an armistice with the enemy, even while thousands of Americans, Koreans and Chinese continued to die. But U.S. ally and South Korean president Syngman Rhee was a fierce critic of the peace talks and opposed any agreement that left Korea divided. In 1953, when a truce agreement was in sight, Rhee jeopardized the settlement by organizing public demonstrations against a deal and threatening to continue the war on his own.

In the fall of 1972, the outlines of a settlement were in place to end the Vietnam War--or, more accurately, to end U.S. involvement in Vietnam. But like Rhee before him, South Vietnam leader Nguyen Van Thieu was deeply skeptical about talks and was outraged with the draft peace settlement. He publicly released an altered version of the deal that made the terms appear even worse than they actually were.

In both Korea and Vietnam, massive U.S. pressure and the full panoply of carrots and sticks were required to win Rhee and Thieu's acquiescence to a deal--and keep the chain gang in lockstep.

Maintaining alliances in Afghanistan while negotiating peace may be even trickier. For one thing, the war is extremely complex with multiple actors pursuing their own agendas. One member of Karzai's High Peace Council commented that: "all the key players...are holding separate and secret talks with their own contacts within the insurgency." With so many cooks, the broth may easily be spoiled.

And there is another reason to worry. The Karzai faction is actually one of the stronger advocates of negotiating with the Taliban--and yet they still sabotaged the discussions.

Other members of America's chain gang are more reluctant to stride toward peace talks. The so-called Northern Alliance, or the non-Pashtun northern groups that helped the United States topple the Taliban back in 2001, are opposed to bringing the Taliban into government--or even negotiating at all.

Amrullah Saleh resigned from the Afghan government in protest at reconciliation with the Taliban, and led a rally of 10,000 in Kabul against a deal--his "anti-Taliban constituency." Saleh hinted that any peace deal might be followed by the re-mobilization of northern forces: "Don't push me to take a gun."