WATCH | Why Trump ordered the killing of Iran's Qassem Suleimani

Shortly after being killed in a US airstrike, analysts believed Iranian General Qassem Soleimani's death changed the rules of engagement between Iran and the US.

He was the head of Iran's elite Islamic Revolutionary Guard Corps (IRGC) Quds Force and the architect of its military and political power.

The Pentagon confirmed that the US military, acting on the orders of the president, was responsible for the airstrike.

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"The US military has taken decisive defensive action to protect US personnel abroad by killing Qasem Soleimani, the head of the Iranian Revolutionary Guard Corps-Quds Force," the Pentagon said in a statement. "This strike was aimed at deterring future Iranian attack plans. The United States will continue to take all necessary action to protect our people and our interests wherever they are around the world."