They argued that it's too risky to withdraw American troops out so quickly, especially with the Afghan presidential election in the balance. They don't want to see Afghanistan go the way of Iraq, and they fear that the Afghan security force, while making substantial gains, won't be ready for solo duty by the end of 2016.
Under Obama's plan, announced in May before Sunni militants seized control of much of Iraq, some 20,200 American troops will leave Afghanistan during the next five months, dropping the U.S. force to 9,800 by year's end. That number would be cut in half by the end of 2015, with only about 1,000 remaining in Kabul after the end of 2016.
Marine Gen. Joseph Dunford, the top U.S. commander in Afghanistan, testified this past week before the Senate Armed Services Committee. He spoke highly of the 352,000-strong Afghan security force that assumed responsibility for the country in June 2013 and lauded them for keeping violence down during the recent election.
"We had over 300 campaign events involving thousands of people, some as large as 20,000," Dunford said. "The Afghan forces secured all of those campaign events."
The U.S. withdrawal plan, however, is based on being able to fix the Afghan security force's shortcomings by the end of 2016.
Dunford described gaps in planning, programming, budgeting, delivering spare parts, fuel payment systems — things the U.S. military takes for granted. Afghanistan also needs to brush up its intelligence operation and develop the nascent air force.
Dunford laid out his best-case scenario under the current plan:
—The Afghan presidential election is resolved.
—Afghan security forces continue to improve and are sustainable by 2017 so a small U.S. presence inside the U.S. Embassy in Kabul — a "security cooperation office" — is sufficient.
—Shortfalls in the Afghan forces are addressed.
—The U.S. and other donor nations continue to fund the Afghan government, security forces and development projects.
—Afghan-Pakistani relations improve and the two nations have adequate capabilities — and the will — to counter terrorism.
His worst-case scenario: The election remains unresolved; Afghan-Pakistan relations sour and both countries fall short of battling extremist militants; al-Qaida or other militant groups regain their footing in the border region and plot attacks against the U.S.
Sen. Lindsey Graham, R-S.C., a critic of Obama's plan, said trying to meet the goals for a successful outcome was like "kicking a 65-yard field goal into the wind."
"There's a disaster in the making to our homeland and to losing all the gains we fought for inside of Afghanistan by drawing down too quick and not being able to help the Afghans in a reasonable fashion," Graham said.