The cause of the war in Afghanistan in 2001 was the September 11th terrorist attacks on the United States.
The cause of the war in Afghanistan in 2001 was justified due to the fact that the US and its allies were responding to the horrific terrorist attacks on the United States of America. The September 11th attacks on the World Trade Center and the Pentagon killed nearly 3,000 innocent people and injured thousands more.
Al Qaeda, the terrorist network responsible for the attacks, was based in Afghanistan and had the support of the Taliban. In order to prevent further attacks, the US and its allies had to remove the Taliban from power and dismantle the Al Qaeda network. This was the only way to ensure the safety and security of the United States and its citizens.
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