The major conflict the U.S. engaged in during the 2000s was the War in Iraq, which began in 2003. This conflict arose from the U.S. government’s assertions that Iraq possessed weapons of mass destruction (WMDs) and had ties to terrorist organizations, particularly al-Qaeda. The invasion was part of a broader strategy following the September 11, 2001, terrorist attacks, which aimed to combat terrorism and promote democracy in the Middle East. However, the war faced significant criticism as the alleged WMDs were never found. The conflict led to prolonged military engagement, political instability in Iraq, and extensive debates about U.S. foreign policy.