The war on terror, officially the Global War on Terrorism (GWOT), is a global military campaign initiated by the United States following the September 11 attacks and is the most recent global conflict spanning multiple wars. The main targets of the campaign are militant Islamist movements like Al-Qaeda, Taliban and their allies. Other major targets included the Ba'athist regime in Iraq, which was deposed in an invasion in 2003, and various militant factions that fought during the ensuing insurgency. After its territorial expansion in 2014, the Islamic State militia has also emerged as a key adversary of the United States.

The cultural influence of the September 11 attacks (9/11) was profound and lasted nearly two decades. The impact of 9/11 extended well beyond geopolitics, spilling into society and culture in general. Many Americans began to identify a "pre-9/11" world and a "post-9/11" world as separable worlds. This created the feeling that the attacks put an end the peacetime prosperity that dominated American life up to that point. Prominent social issues at the time, such as the public discourse in the wake of the Columbine High School massacre, became overshadowed by the attacks. Following 9/11, the attention of most Americans shifted from domestic issues towards terrorism abroad.