The US took immediate action to address the 9/11 attacks, ordering all civilian aircraft to land and implementing DEFCON 3.
Rescue efforts were launched to save survivors and recover victims from the Pentagon and the World Trade Center.
The US formed alliances, such as the Northern Alliance, to combat the Taliban regime in Afghanistan.
President George Bush declared a global war on terror and sought UN support for military action.
The US launched airstrikes against Taliban positions and partnered with anti-Taliban forces in Afghanistan.