September 11 terror attacks
Almost 7 trillion dollars spent by US on defense since 2001 went to private companies

A study by the Costs of War project notes that the policy of involving private players in the defense sector has led to the undermining of attempts to seek diplomatic solutions. It has also led to the invention of new threats to keep the defense budget extraordinarily high 

20 years of the ‘War on Terror:’ Horrific costs, no end in sight

Successive US administrations used the tragedy of September 11, 2001, to pursue endless wars which achieved nothing but death of millions of people and destruction of countries such as Afghanistan, Iraq and Syria

20 years of ‘war on terror’ have caused nearly a million deaths, says report

The overall estimate of the monetary cost of the war goes beyond USD 8 trillion by the US alone. Its allies, including the UK, Australia, and Germany, would have spent a greater amount collectively