President Bush was referring to the terrorist attack to the World Trade Center twin towers on 09/11/2001, in which 4 airplanes filled with civilian passengers kidnapped by a total of 19 terrorists were intentionally led to collide with strategically important commercial and governmental buildings.
The first 2 planes were led to hit each of the twin towers, which caused them to fully collapse 2 hours after the impact. The third hit the Pentagon, and the forth was unsuccessful due to an attempt of retaking control by passengers and crew members. It was on its way to Washington DC when it fell at an open field close to Shanksville, Pennsylvania.
None of the passengers on board of the planes survived, and the total deaths count reaches close to 3000, among which citizens of more than 70 different nations.
The attacks were claimed by the terrorist islamic organization Al-Qaeda led and found by the infamous terrorist Osama bin Laden, at the time. The US immediate international course of action was the launch of the War on Terror (a.k.a. Global War on Terrorism) started by an invasion to Afganistan, in order to take down the Taliban (group that was harboring the Al-Qaeda terrorists in the country). Along with the war, the US approved the USA Patriot Act, as a domestic act, which allows the government, among other things, to intercept phone calls and e-mails between organizations and people (american or foreign) with suspicion to be somehow related to terrorism, without any need of Justice approval. Many other great nations also reinforced their antiterrorist legislation and expanded the law reach towards the matter.
