The number of American troops in Iraq has fallen below 50,000 for the first time since the US-led invasion more than seven years ago. The US now has 49,700 troops in Iraq, and plans to maintain that level through next summer, according to General Ray Odierno, the head of US forces in Iraq. They have been dubbed "advisory and assistance brigades," responsible for training Iraqi forces and conducting joint missions. US officials say the troops will no longer conduct independent missions after August 31, though they will be fully armed and allowed to defend themselves. "We've met our goal," Odierno said. "But the story is not about 50,000. The story is that we are continuing to be committed to Iraq. But our commitment is going to change." Odierno, too, will leave Iraq shortly: He will turn over command to his successor, General Lloyd Austin, on September 1.Odierno's "goal" was established by Obama in February 2009, when he announced in a speech that the US would withdraw all combat troops from Iraq by the end of August 2010. It is the second of three major milestones on the road to an (almost) complete US withdrawal. The first came in June of last year, when US forces withdrew from Iraqi cities and towns; the last will come in December 2011, when the US is required to end its occupation of Iraq. Both of those milestones were established by the status-of-forces agreement, a document negotiated in 2008 by the US and Iraqi governments.