US President George W. Bush has landed in Iraq on a surprise farewell visit - a last stop for him in a country that has defined his presidency and a chance to celebrate a new security pact with Iraqi leaders. Under intense security, Air Force One landed Sunday afternoon local time at Baghdad International Airport. The president left Washington on Saturday night on the 11-hour flight. The visit is Bush's fourth to the war zone as president and it's his last before he hands management of the war over to US President-elect Barack Obama. As with Bush's three previous trips to Iraq, this one was conducted under a strict cloak of secrecy. The security situation in Iraq has improved, but it still is considered risky.