The United States said on Wednesday, September 30, that it had completed the withdrawal of its troops from Iraq, more than 20 years after the invasion that toppled Saddam Hussein.

U.S. Central Command described an orderly departure that ends a 12-year military presence that began with the war against the Islamic State group. For years, about 2,500 American troops had been stationed in the country.

Washington and Baghdad had agreed on the September 30 deadline, reaffirming it during Iraqi Prime Minister Ali al-Zaidi's visit to Washington.

Iraq's government is marking the exit with four days of national holiday, called Sovereignty Days, from September 30 to October 3. Iran and its allies in Iraq also celebrated, while Kurdish leaders voiced concern about what comes next.

Analysts warn that the departure could embolden Iran-backed militias and give the Islamic State room to regroup.