"I think Obama has fallen into a trap laid for him by generals... I think it's a fateful decision and it could determine whether he's a one-term president."
But Larry Korb, a former assistant secretary of defence, described Obama's speech as "a masterful job."
Korb highlighted the parts of the address where Obama described the US operation in Afghanistan as time-limited and as seeking a partnership with the Afghans.
"I think it's a fateful decision and it could determine whether he's a one-term president."
Tariq Ali, historian
and political activist
"One of the most interesting things he said [to the Afghan people] was that we're your partner, not your patron. In the final hours it's going to have to be up to you.
"At the end of a speech, when he said the US doesn't have the resources for an open-ended commitment and can't solve all the world's problems, it also was a message to Karzai: 'I would like you to take more control more in the next 18 months.'"
Nasrine Gross, an Afghan women's activist based in Washington, also stressed the need for co-operation with Afghans.
"The voice of the Afghan people needs to be heard, the government of Afghanistan needs to be worked with in such a way that not only corruption gets decreased but also services are delivered to ordinary people.
"I'm very happy that the troops are finally going... The troops are very needed. If the troops are not there, the people of Afghanistan are suffering too much."
However, Mike Honda, a Democratic congressman, voiced concerned over how the troops will be paid for, and called for a war tax.
"Every war we've been engaged in, we've always had a tax attached to it. But since we went into Iraq in 2003, we've had no war tax to support the effort. We've been borrowing against our budget.
"That's why our deficit and our debts have increased... If we're going into Afghanistan with 30,000 more troops, let's pay for it through a war tax so that it's not going to increase our debt."