The Iraq war was a response to the Al Qaeda bombing of the twin towers in New York City in September 2001.
The Iraq War was an armed conflict which started with an invasion of Iraq in 2003, one led by the United States. This invasion was responsible for toppling the government at the time, controlled by Saddam Hussein. The conflict did not stop there, continuing for most of the following decade. This conflict continued due to the emergence of insurgency forces who opposed the occupation by American forces. The United States made its official withdrawal in 2011, but this insurgency continues to different degrees.
The invasion started in March of 2013. The United States enjoyed support from the United Kingdom and other coalition allies to launch surprise attacks without an official declaration of war. These attacks were intended to shock and awe the enemy. The forces of the Iraqi army were overwhelmed, allowing the United States forces to sweep throughout the country. The invasion brought down the Ba’athist government. In December of 2003, Saddam Hussein was captured and after a military court trial in America he was executed.
However, a power vacuum took place after his demise and the occupation was overall poorly managed. This led to widespread violence between the Sunnis and the Shias. It also led to a long insurgency against the coalition and American forces. The response by the United States was to send in more troops in 2007. The heavy security presence began to make deals with Sunni militias and with occupying forces in an effort to bring down the high escalation of violence. The number of troops on the ground were slowly withdrawn between 2007 and 2008 leading to the formal withdrawal of 2011.
The rationale for the war by the Bush administration was that Iraq was the owner of weapons of mass destruction and that the government of Saddam Hussein posed a direct threat to the United States and its allies. Some officials went so far as to accuse Saddam of supporting al-Qaeda and harboring some of their officials. By the end of the war, no evidence in support of any of those claims were found. Soon after, a long investigation took place the results of which found that pre-war intelligence had been misrepresented. Heavy criticism was faced by the United States both at home and abroad for what some deemed a poorly planned response to a significant terror threat.