BAGHDAD — The last convoy of American troops drove into Kuwait on Sunday morning, punctuating the end of the nearly nine-year war in Iraq.

As an indication of the country the United States is leaving behind, for security reasons the last soldiers made no time for goodbyes to Iraqis with whom they had become acquainted. To keep details of the final trip secret from insurgents — or Iraqi security officers aligned with militias — interpreters for the last unit to leave the base called local tribal sheiks and government leaders on Saturday morning and conveyed that business would go on as usual, not letting on that all the Americans would soon be gone.

The crossing brought a close to a final troop withdrawal drawn out over weeks of ceremonies in Baghdad and around Iraq, including a formal if muted flag-folding ceremony on Thursday, as well as visits by Vice President Joseph R. Biden Jr. and Defense Secretary Leon E. Panetta, and a trip to Washington by Prime Minister Nuri Kamal al-Maliki.

The last troop movement out of Iraq, which included about 110 vehicles and 500 soldiers, began in darkness. Around 2:30 a.m., the convoy snaked out of Contingency Operating Base Adder, near the southern city of Nasiriya, and headed toward the border.