Iran has launched strikes against US troops in Iraq.
If you're not sure exactly what's going on, or why this is happening, this is the perfect place to start.
Let's get you up to speed and answer five quick questions about the situation.
1. What has happened?
Iran has confirmed it launched "tens" of surface-to-surface missiles at two military bases — Al Asad and Irbil in Iraq — that house US troops.
The Pentagon says the bases came under fire from "at least a dozen ballistic missiles" and it was clear the missiles were launched from Iran.
The US and Iraq both confirmed their forces did not suffer casualties from the strikes. Germany, Denmark, Norway and Poland also said none of their troops in Iraq were hurt.
2. Why has this happened?
On January 4, the United States killed Iran's most powerful military general, Qassem Soleimani, by firing three missiles at Baghdad airport.
General Soleimani was the leader of Iran's elite Quds Force and responsible for many of the nation's proxy wars in the Middle East.
In a statement after the attack, the Pentagon said the strike was aimed at "deterring future Iranian attack plans" and it carried out the attack to "protect US personnel abroad".
For context, academic Ranj Alaaldin described the attack as "bigger than taking out Osama bin Laden".
On Tuesday millions of people attended funerals for General Soleimani, the first time Iran honoured a single person with a multi-city ceremony.
Go deeper:The ABC's Matt Brown has a long look at the importance of General Soleimani, and the "watershed moment" of his death, in this piece here.
3. Is this actually the start of World War III?
It's far too early to tell what might happen next, despite #WorldWarThree trending on social media in the days since the US killed General Soleimani.
Journalist with Al Jazeera based in Doha, and a former global affairs and Indigenous affairs analyst for the ABC, Stan Grant, wrote that Iran was dwarfed by the United States by any measure.
"Its population is a quarter the size of America's, its economy is barely 2 per cent as large. Its outdated weapons are no match for the most powerful military force the world has ever known," he wrote.
There are many moving parts to this story that are yet to play out, but Grant writes that World War III will look vastly different to World War I and II.
"A look around the world tells us we may already be in it," he writes.
Get the full picture:You can read his full analysis of the situation here.
4. Are any Australians involved?
Prime Minister Scott Morrison said all Australian Defence Force and diplomatic personnel in Iraq were safe.
Mr Morrison said the Australian Government was monitoring the situation as it unfolds.
Australia's National Security Committee is scheduled to meet on Thursday, but Mr Morrison said it would meet earlier if needed.
Opposition Leader Anthony Albanese said he had received a briefing on the situation from the Prime Minister, and said Australians were "located very close to where the Americans are located in the area".
"They're just next door," Mr Albanese said.
5. What will happen next?
The frustrating answer is — we just don't know. And we can't do much but wait.
All eyes now turn back to the United States.
At a news conference, President Donald Trump said Iran appeared to be "standing down" and declared the US would impose further economic sanctions on the Iranian regime.
"The fact that we have this great military and equipment, however, does not mean we have to use it. We do not want to use it. American strength, both military and economic, is the best deterrent," he said.
He added that Americans should be "extremely grateful and happy" with the outcome.
Crucially, Mr Trump stopped short of making any more threats of military actions.