The United States will deploy thousands of additional soldiers to the Middle East following the death of Maj Gen Qasem Soleimani.
Soleimani was the leader of Iran's Quds Force, a security group which organised and enforced operations outside of Iran in countries like Iraq and Syria. He was widely regarded as one of Iran's most powerful men and a designated terrorist by the US.
On Friday (NZT), he was killed in an airstrike on Iraq's Baghdad airport, which also killed militia leader Abu Mahdi al-Muhandis.
The killing, carried out at the direction of US President Donald Trump, has sent shockwaves across the world, with Iran expected to respond harshly. Already, Iran's Supreme Leader Ayatollah Ali Khamenei has vowed revenge and "harsh vengeance". Al Jazeera has also reported that the new leader of the Quds Force, Ismail Qaani, has promised "bodies of Americans all over the Middle East".
The threatened response has prompted dozens of US citizens in the Iraqi oil city of Basra to flee while the US Embassy in Iraq has told Americans to "depart Iraq immediately" and not approach the embassy.
Due to its proximity to Iran and as the location of the assassination, Iraq could become a centre of the conflict. Iranian-backed militia are believed to be all over Iraq and attacked the US Embassy last week.
The US will deploy roughly 3000 additional soldiers to the Middle East in case of attacks. Officials anonymously told CNN that these would be in addition to the 700 soldiers sent to Kuwait earlier this week after the embassy attacks.
Since May, there have been about 14,000 extra troops sent to the Middle East.
Despite the beefed-up security abroad, the US' acting Homeland Security said there are no "specific, credible threats against our homeland".
"The entire Department remains vigilant and stands ready, as always, to defend the homeland," said Chad Wolf.
The Trump-directed attack comes after a week of heightened tension between Iran and the US. Last week, an American contractor in Iraq was killed in a rocket attack which the US has blamed on Iranian-backed militia. In response, the US killed 25 Kataeb Hezbollah fighters, leading militias to attack the US Embassy in Baghdad.
A statement from the Pentagon on Friday said Soleimani was also actively developing plans to attack American diplomats and service members in Iraq and throughout the region. The general was blamed by the US for the deaths of hundreds of Americans.
"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."
While it was welcomed by many who supported Trump acting decisively, others - including many Democratic Presidential nominee candidates - have said it was an uneducated move that risks Americans' safety.
"Trump's dangerous escalation brings us closer to another disastrous war in the Middle East that could cost countless lives and trillions more dollars," said Bernie Sanders.
Protests have also broken out in Iran upon news of Soleimani's death, with scores of people taking to the streets crying.