In less than six months, the 45,000 US troops still deployed in Iraq will leave the country. When the US led the invasion of Iraq beginning on March 20, 2003, it had a force of 150,000 American troops and 23,000 soldiers from other countries.
After Baghdad fell 20 days later, US troop levels dropped to around 127,000 by June 2006, with 20,000 soldiers from coalition countries. But as violence again escalated in January 2007, George Bush, the US president, proposed sending another 21,500 troops.
By October there were 171,000 American fighters in the country and 12,000 soldiers from other nations.
In February 2009, the newly elected US president, Barack Obama, announced that the US combat mission in Iraq would end by the end of August 2010. Withdrawals began in June 2009.
Now there are still around 45,000 American troops in Iraq, responsible for training Iraqi forces. But for Iraq's Kurds, the scheduled withdrawal is a big concern, as they try to resolve disputes over territory.
Watch the second of a four-part series on Iraqi security by Al Jazeera's Omar Al Saleh, followed by an interview with Mamdouh Salameh, an international oil economist based in London.