Why did Britain go to war with Al-Qaeda?

Britain went to war with Al-Qaeda primarily in response to the September 11, 2001, terrorist attacks in the United States, which prompted a global counter-terrorism campaign. The UK government viewed Al-Qaeda as a significant threat to national and international security, leading to military involvement in Afghanistan to dismantle Al-Qaeda's operations and remove the Taliban regime that harbored them. This commitment was also in line with Britain's longstanding alliance with the United States and the need to combat extremism.