"John McCain voted against funding for the troops," as well, Biden countered, adding that the Republican presidential candidate had been "dead wrong on the fundamental issues relating to the conduct of the war."
Biden did not immediately reply to Palin's mention of his son, Beau, the Delaware attorney general, who is scheduled to fly to Iraq with his National Guard unit on Friday.
Palin has a young son who is in Iraq with the Alaska National Guard, although she did not refer to it.
The exchange over Iraq was easily the most personal, and among the most pointed, as the two running mates debated across 90 minutes on a stage at Washington University.
They also clashed over energy, the economy, global warming and more in their only debate, with little more than one month remaining in the campaign and McCain struggling to regain his footing.
Republican officials disclosed earlier in the day that he was conceding the battleground state of Michigan to Obama. The state voted Democratic four years ago, but McCain had spent millions trying to place it in his column.
Biden was scathing in his criticism of McCain's position on the Iraq war, calling him erns.
He readily agreed she could - and she used it to effect more than an hour later. "Say it ain't so, Joe," she said as she smilingly criticized him at one point for focusing his comments on the Bush administration rather than the future.
She made only one obvious stumble, when she twice referred to the top U.S. general in Afghanistan as "Gen. McClellan." In fact, his name is David McKiernan.
Biden's burden was not nearly as fundamental. Although he has long had a reputation for long-windedness, he is a veteran of more than 35 years in the Senate, with a strong knowledge of foreign policy as well as domestic issues.
For much of the evening, the debate unfolded in traditional vice presidential fashion - the running mates praising their own presidential candidate and denigrating the other.
Palin said Obama had voted to raise taxes 94 times - an allegation that Biden disputed and then countered. By the same reckoning, he said, McCain voted "477 times to raise taxes."
They clashed over energy policy, as well, when Palin said Obama's vote for a Bush administration-backed bill granted breaks to the oil industry. By contrast, she said that as governor, she had stood up to the same industry, and noted that McCain had voted against the bill Obama supported.
Biden said that in the past decade, McCain had voted "20 times against funding alternative energy sources and thinks, I guess, the only answer is drill, drill, drill."
"The chant is, `drill, baby drill," Palin countered quickly, unwilling to yield to Biden on that issue - or any other.
On the environment, Palin declined to attribute the cause of climate change to man-made activities alone. "There is something to be said also for man's activities, but also for the cyclical temperature changes on our planet," she said, adding that she didn't want to argue about the causes.
Biden said the cause was clearly man-made, and added, "If you don't understand what the cause is, it's virtually impossible to come up with a solution."
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