What you need to know about rising tensions between the U.S. and Iran after Soleimani death

William Cummings | USA TODAY

Show Caption Hide Caption Are we really ready for a World War III? Fears are mounting around the world following the assassination of Iranian General Qasem Soleimani - but is World War 3 about to happen?

WASHINGTON – Tensions between the U.S. and Iran are at one of highest points since the 1979 Iranian revolution following Iran's attacks Tuesday night on U.S. and coalition forces in Iraq.

Iran fired more than a dozen missiles at U.S. troops and coalition forces at two bases in Iraq an apparent retaliation for a U.S. drone strike days earlier that killed one of Tehran's most powerful officials, Gen. Qasem Soleimani.

Though the extent of the damage was not immediately clear, the attack represented a major escalation of tension between Tehran and Washington that had already been boiling over for months. Both President Donald Trump and Iranian officials have threatened further reprisals if either side attacks.

Click 'play' above to hear about the House vote to limit Trump's war powers.

Here is what you need to know about the situation former CIA Director Leon Panetta described as "closer to war with Iran than we’ve been in the last 40 years."

How we got here

U.S. and Iranian hostilities have been mounting since Trump took office and began a "maximum pressure" campaign on the regime. He pulled out of the deal that offered sanctions relief in exchange for a delay in Iran's nuclear weapons program. Since then, the U.S. has blamed Iran for attacks on oil tankers and Saudi oil refineries, as well as the downing of an American drone.

On Dec. 27, a barrage of rockets killed an American contractor and wounded four U.S. service members on a base in northeastern Iraq. The U.S. blamed the attack on an Iranian-backed militia with ties to Iran's elite Quds Force led by Soleimani and responded Dec. 29 with strikes on five targets in Iraq and Syria that left at least two dozen militia fighters dead.

Angry protesters led by a larger umbrella group of Shiite militias answered that attack by storming the U.S. Embassy in Baghdad. They forced their way into the compound and set fire to a reception area before eventually being driven off by security forces on Tuesday. There were no casualties in the embassy breach, which Secretary of State Mike Pompeo called an "Iran-backed terrorist attack."

Early Friday morning, Soleimani was killed in a U.S. drone strike at the airport in Baghdad. Administration officials said Soleimani was plotting attacks on Americans in the Middle East and that he presented an imminent threat.

'I want to have peace': How Trump went from a vow to avoid conflict to an order to kill Iran general

More: Pompeo blames current tension with Iran on 'Obama administration’s appeasement'

Who was Soleimani?

Retired Gen. David Petraeus, who counted Soleimani as a "very capable" adversary during his time commanding U.S. troops in Iraq, told CBS News, "It's impossible to overstate the significance of the attack" that killed the 62-year-old Iranian general, the leader of Iran's Quds Force.

"This is bigger than bin Laden. It's bigger than Baghdadi," he said of the death of the man behind Iran's intelligence and military strategy.

The Quds Force headed by Soleimani since the late 1990s is part of the Islamic Revolutionary Guard Corps, which Trump designated a foreign terrorist organization in April, the first time an official branch of a foreign government was given that label. Under Soleimani, the irregular Quds Force trained and supported militias loyal to Tehran throughout the Middle East.

The U.S. says the Quds Force began training Iraqi militants to kill American troops in Iraq after the 2003 invasion and taught them how to make powerful roadside bombs.

The U.S. blames Soleimani for 603 U.S. service members killed in Iraq, in addition to thousands of others in the region.

Iran official on Soleimani killing: 'The response for a military action is military action'

How did Iran respond?

After Soleimani's death, Iran's Supreme Leader Ayatollah Ali Khamenei said "forceful revenge awaits the criminals who have his blood ... on their hands." The regime has promised "harsh retaliation" is coming.

Iran launched missile attacks on Ain Assad air base, which is located in western Iraq and was used by American forces after the 2003 U.S.-led invasion that toppled dictator Saddam Hussein. It houses about 1,500 U.S. and coalition forces. The Irbil military base, which the Pentagon said was the site of another attack, is located in Iraq's semiautonomous Kurdish region.

Experts say cyberattacks on U.S. and increased disruption of the oil supply are other possible ways Iran might retaliate.

On Sunday, hundreds of thousands of Iranians took to the streets to mourn Soleimani as his body was brought home for burial.

That same day Iran announced it was effectively withdrawing from the nuclear deal Trump pulled out of last year. Trump had long derided the deal, which was brokered by the Obama administration, but several European nations, as well as China and Russia, were still party to the agreement intended to stave off Iran's development of nuclear arms for at least 10 years.

How did Iraq respond?

Iraqi Prime Minister Adel Abdul Mahdi decried the U.S. strike that killed Soleimani and the ones that targeted militia fighters as attacks on Iraq's sovereignty and said it was "time for American troops to leave" after more than 16 years.

Iraq's parliament agreed and voted Sunday in favor of a nonbinding resolution calling for U.S. troops to leave the country.

Trump said the U.S. would not leave unless Iraq repaid the government for an "extraordinarily expensive airbase." He said if Iraq tried to kick U.S. forces out, he would "charge them sanctions like they’ve never seen before ever."

What was the imminent threat?

Pompeo has said Sunday that the administration made the "right decision" because Soleimani was preparing for what was "going to be a significant attack," but details about the threat have not been made public.

Sen. Marco Rubio, R-Fla., said Trump was forced to act in the face of "information that there is an imminent and credible threat that could cost the lives" of "potentially hundreds, if not thousands, of American servicemen and women and other personnel in the region."

But congressional Democrats were not as certain.

House Intelligence Committee Chairman Adam Schiff, D-Calif., agreed it was "accurate" to say Soleimani was plotting against American interests.

"But it's also true that Soleimani has been plotting against the United States for decades. The question is, did the plotting here rise to the level that required his elimination from the battlefield?" Schiff said. "I don't think the intelligence supports the conclusion that removing Soleimani increases our security."

"I accept the notion that there was a real threat," Sen. Mark Warner, D-Va., said on NBC's "Meet the Press." "The question of how imminent is something that I need more information on."

How has Congress reacted?

Democrats have complained that Trump did not inform leaders on Capitol Hill before taking action, as president have done ahead of other military moves in recent years.

Trump sent Congress a document on Saturday informing lawmakers of his military action as required by the War Powers Act of 1973, and on Sunday he posted an apparently mocking tweet, which he said "will serve as notification" that he will strike Iran if the country attacks "any U.S. person or target."

House Speaker Nancy Pelosi, D-Calif., said the document sent by Trump "prompts serious and urgent questions about the timing, manner and justification of the administration’s decision to engage in hostilities against Iran."

Sen. Tim Kaine, D-Va., introduced a resolution barring the use of further military force against Iran without congressional authorization. On Sunday, Reps. Ilhan Omar, D-Minn., and Barbara Lee, D-Calif., announced they planned to introduce a House version of the resolution.

"Let’s not mince words: the assassination of Qasem Soleimani was an act of war undertaken without Congressional authorization, in violation of the Constitution of the United States of America," they said in a statement.

Pelosi said the House will vote on the resolution this week.

More: Nancy Pelosi says House will vote to limit Trump's war powers on Iran as tensions grow

What has Trump said?

In a series of belligerent tweets, Trump has warned that any further action against the U.S. would lead to strikes on "Iran itself.'

He said the U.S. had identified 52 targets "representing the 52 American hostages taken by Iran many years ago." Trump said cultural sites were among the potential targets, which critics said would constitute a war crime.

Though Pompeo said the U.S. would only hit "lawful" targets, Trump repeated his threat while speaking to reporters on board Air Force One.

"They’re allowed to torture and maim our people. They’re allowed to use roadside bombs and blow up our people,” Trump said. "And we’re not allowed to touch their cultural site? It doesn’t work that way."

They attacked us, & we hit back. If they attack again, which I would strongly advise them not to do, we will hit them harder than they have ever been hit before! https://t.co/qI5RfWsSCH — Donald J. Trump (@realDonaldTrump) January 5, 2020

Contributing: Kim Hjelmgaard, Courtney Subramanian, John Fritze, David Jackson, Nicholas Wu and Savannah Behrmann, USA TODAY; The Associated Press