Ryan hit Biden hard on failing to secure an agreement with the Iraqi government to keep some U.S. troops in the country.

Obama campaigned on a pledge to conclude the U.S. military role in Iraq, and he did that by withdrawing all U.S. forces at the end of 2011. He has made doing so a key part of his stump speech when discussing his foreign policy achievements. Biden was given chief responsibility for Iraq policy inside the administration.

But Romney, among other Republicans, has accused Obama of failing to secure an agreement with the Iraqi government that would have allowed the U.S. military to keep thousands of troops in Iraq beyond the 2011 deadline, which was set by the George W. Bush administration. Romney has said those troops may be needed if sectarian tensions inside the country develop into a civil conflict.

It is true Obama did not secure such an agreement. The main stumbling block was the refusal of the Iraqi parliament to grant U.S. forces immunity from Iraqi prosecution for any alleged crimes committed there beyond the 2011 deadline.

It is also true Obama, eager to fulfill his campaign pledge, was not overly eager to maintain forces in Iraq at a time of rising debt at home and a troop surge in Afghanistan. Romney has called the departure a failure of Obama’s leadership, even though much of the country supported the move.

“The vice president was put in charge of those negotiations and he failed to get an agreement,” Ryan said.

Biden countered that nothing Ryan said was accurate.