Addressing soldiers and civilians at Bagram air base near Kabul, he thanked them for their service and said they would prevail against their enemies.
They were there, he said, to "keep America safe and secure".
On a trip lasting just a few hours, he met Afghan President Hamid Karzai and stressed the need to tackle corruption.
Mr Obama said he wanted to see progress continue on Afghan efforts to fight against drug-trafficking.
Mr Karzai will visit the US in May for talks, it was announced.
In December, Barack Obama ordered the deployment of an extra 30,000 US troops to Afghanistan.
Only a few thousand of the extra forces have arrived so far, with most expected to be in place by the summer.
Shortly after his speech to the troops, the US president, who is travelling on his Air Force One jet, left the country.
'Thank you'
US troops make up the majority of the Nato-led coalition force in Afghanistan.
Speaking to the large indoors gathering at Bagram, Mr Obama said: "There is no visit that I consider more important than this visit I am making now.
"My main job here today is to say thank you on behalf of the entire American people."
He added: "The Afghans have suffered for decades, decades of war, but we are here to help Afghans forge a hard-won peace... and we want to build a lasting partnership founded upon mutual interest and mutual respect."
Mr Obama said America had not chosen the war, and had not sought to meddle in Afghan affairs or expand its influence.
It had, he said, been "attacked viciously on 9/11", and al-Qaeda leaders and their Taliban allies were still in the region and had to be defeated.
The US aimed to deny al-Qaeda a safe haven and reverse the Taliban's momentum, he said.
He promised troops that they were being "backed up by a clear mission and the right strategy" and that they would have "the support to get the job done".
"I'm confident all of you here are going to get the job done in Afghanistan," he said to applause and cheers.
Posts
I like the Easter Bunnies
ReplyDelete