Question

As a result of the terrorist attacks on September 11, 2001,

Answer 1

As a result of the terrorist attacks on September 11, 2001, the international community which were well-represented by their respective governments vowed to protect their citizens against terrorism. These governments passed legislation to fight terrorism. Terrorism has been tackled more severely ever since. 

Answer 2

As a result of the terrorist attacks on September 11, 2001, the US declared a "war on terror."

Following the terrorist attacks perpetrated by al-Qaeda on September 11, 2001, the Bush administration declared a worldwide "war on terror," involving open and covert military operations, new security legislation, efforts to block the financing of terrorism, and the like. Washington urged other states to join in the fight to oppose to terrorism claiming that "either you are with us, or you are with the terrorists."