The new century opened with trauma. On September 11, 2001, the al-Qaeda terrorist attacks on the United States killed nearly three thousand people and prompted a U.S.-led invasion of Afghanistan later that year to oust the Taliban and dismantle al-Qaeda's bases. In March 2003, a U.S.-led coalition invaded Iraq, toppling Saddam Hussein but unleashing years of instability. The post-9/11 era also saw the rise of popular protest movements, beginning in 2010 with the Tunisian revolution that inspired what became known as the Arab Spring, a wave of pro-democracy uprisings across the Arab world. In Egypt, Mohamed Morsi rose briefly to power before a coup brought Abdel Fattah el-Sisi to the presidency, while Syria descended into a devastating civil war that began in 2011 and continued for years afterward.
Europe faced its own reckoning. In 2016, the United Kingdom voted to leave the European Union, a process known as Brexit, formally completed on January 31, 2020. Just weeks later, the World Health Organization declared COVID-19 a global pandemic in March 2020, triggering a worldwide health and economic crisis whose consequences are still being felt. In the post-Soviet space, the color revolutions of the early 2000s and 2010s, including Ukraine's Orange Revolution (2004–2005) and the Euromaidan (2013–2014), signaled persistent struggles for political direction. Russia annexed Crimea in 2014 after a contested referendum, and on February 24, 2022, launched a full-scale invasion of Ukraine, the largest European war since 1945, a conflict whose outcome will shape the international order for decades to come.