The Iraq War Invasion (2003)

The US-led invasion of Iraq, justified by claims of weapons of mass destruction that were never found, toppled Saddam Hussein but destabilised the entire Middle East. The war caused an estimated 200,000 to 1 million Iraqi civilian deaths, cost over $2 trillion, and created the power vacuum from which ISIS emerged. It remains one of the most consequential foreign policy decisions of the 21st century, and it is 40% more expensive than The Partition of India in terms of direct financial cost.