Top Iranian forces commander and architect of military operations, Qasem Soleimani, was killed early Friday in Baghdad by a drone strike ordered by US President Donald Trump, the Pentagon announced.

Suleimani, leader of the US-designated Foreign Terrorist Organization Quds Force of the Islamic Revolutionary Guards Corps and top commander of Iranian security and intelligence operations, was hit by the drone strike while being driven to the Baghdad International Airport by local allies of the Popular Mobilisation Forces (PMF). Also killed in the attack was Abu Mahdi al-Muhandis, leader of the PMF.

According to the Pentagon statement, Trump ordered the strike as a “decisive defensive action” to deter further attacks by the Iranians.

General Soleimani was actively developing plans to attack American diplomats and service members in Iraq and throughout the region. General Soleimani and his Quds Force were responsible for the deaths of hundreds of American and coalition service members and the wounding of thousands more. He had orchestrated attacks on coalition bases in Iraq over the last several months—including the attack on December 27th—culminating in the death and wounding of additional American and Iraqi personnel.

The strike killing Suleimani is the latest in an escalation of tensions between Washington and Tehran and follows one week after the rocket attack on an Iraqi military base that killed an American contractor.

Iran’s supreme leader, Ayatollah Ali Khamenei, responded to the attack Friday, declaring “a forceful revenge” awaits the US. The statement, published by Fars News Agency, also declared a three-day mourning period for Suleimani.

Late Thursday, amid reports of the strikes hitting in Iraq and ahead of the Pentagon’s statement, Trump tweeted a picture of the American flag with no text.