(CNN) Days after President Donald Trump ordered a drone strike that killed Qasem Soleimani , the powerful commander of Iran's elite Quds Force, the United States is bracing for possible retaliatory actions by Iran. The military adviser to Iran's Supreme Leader told CNN on Sunday that Tehran will certainly strike back against US "military sites."

Here's how tensions between the two nations have escalated in recent weeks:

December 27

December 29

According to the Pentagon, US forces conducted airstrikes at five facilities in Iraq and Syria controlled by a Shiite military group known as Kataib Hezbollah. American officials have blamed the group for attacks on US-Iraq military facilities, including the one that killed the US civilian contractor two days earlier near Kirkuk.

At least 25 people were killed in the US airstrikes, the Popular Mobilization Units, a Tehran-backed Shiite militia also known as Hashd al-Shaabi, said in a statement.

Before the airstrikes, the United States had been pushed to the brink of retaliation against Iran or its proxies, specifically after attacks last summer on oil tankers in the Persian Gulf and oil facilities in Saudi Arabia and Iran's downing of a US drone in June.

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December 31

Pro-Iranian protesters attacked the US Embassy in Baghdad , scaling walls and forcing the gates open. The protesters were demonstrating against the American airstrikes on the Iran-backed militia group in Iraq. Trump threatened Iran, warning the country's leaders would be held responsible for any death or destruction after the attack.

The United States deployed 750 troops from a unit in Fort Bragg, North Carolina, to protect the embassy.

Protesters stand on walls at the US Embassy in Baghdad on December 31.

January 3

Trump said he ordered a precision drone strike at the Baghdad airport to "terminate" Soleimani, a top Iranian commander who was plotting "imminent and sinister attacks on Americans diplomats and military personnel." Others were killed in the attack.

"We took action last night to stop a war. We did not take action to start a war," Trump said in a statement from his Mar-a-Lago resort in Florida.

The Pentagon has blamed Soleimani and his Quds Force for attacks on coalition bases in recent months, including the December 27 strike and the attack on the US Embassy in Baghdad. The United States began deploying thousands of additional troops to the Middle East -- on top on the 750 -- from the same unit in Fort Bragg as tensions mounted.

Photos: US airstrike in Baghdad kills Iran's top general Mourners throng the car carrying the body of Iranian commander Qasem Soleimani during a funeral procession for Soleimani and Iraqi paramilitary leader Abu Mahdi al-Muhandis in Baghdad on January 4. Hide Caption 1 of 22 Photos: US airstrike in Baghdad kills Iran's top general Mourners touch a casket draped in Iranian flags during Qasem Soleimani's funeral procession on January 4. Hide Caption 2 of 22 Photos: US airstrike in Baghdad kills Iran's top general This photo, released by the Iraqi Prime Minister Press Office, shows a burning vehicle at the Baghdad International Airport following the US airstrike that killed Gen. Qasem Soleimani, the head of Iran's elite Quds Force, on January 3. Hide Caption 3 of 22 Photos: US airstrike in Baghdad kills Iran's top general People watch debris burn near the airport after the airstrike on January 3. Hide Caption 4 of 22 Photos: US airstrike in Baghdad kills Iran's top general Pro-Iranian militiamen and their supporters set a fire while US soldiers shoot tear gas during a demonstration outside the US Embassy in Baghdad, Iraq, on Wednesday, January 1. Hide Caption 5 of 22 Photos: US airstrike in Baghdad kills Iran's top general A protester inspects the burnt-out entrance of the US Embassy on January 1. Hide Caption 6 of 22 Photos: US airstrike in Baghdad kills Iran's top general US Marines stand guard on the roof of the US Embassy while protesters demonstrate on Wednesday. Hide Caption 7 of 22 Photos: US airstrike in Baghdad kills Iran's top general Protesters set fire to a reception room of the US Embassy in Baghdad, Iraq, on Tuesday, December 31. The embassy was attacked during demonstrations in response to recent airstrikes in Iraq and Syria conducted by US forces. Hide Caption 8 of 22 Photos: US airstrike in Baghdad kills Iran's top general US Marines from a crisis response task force based in Kuwait prepare to deploy to Baghdad to bolster security at the embassy. Hide Caption 9 of 22 Photos: US airstrike in Baghdad kills Iran's top general A US Army Apache helicopter drops flares over Baghdad in a show of force. Hide Caption 10 of 22 Photos: US airstrike in Baghdad kills Iran's top general Protesters carry the logo of the US Embassy. Hide Caption 11 of 22 Photos: US airstrike in Baghdad kills Iran's top general Smoke billows from a sentry box at an entrance of the embassy. Hide Caption 12 of 22 Photos: US airstrike in Baghdad kills Iran's top general Protesters throw stones toward the embassy. Hide Caption 13 of 22 Photos: US airstrike in Baghdad kills Iran's top general US soldiers take positions around the embassy during the protests. Hide Caption 14 of 22 Photos: US airstrike in Baghdad kills Iran's top general Protesters burn property in front of the embassy compound. Hide Caption 15 of 22 Photos: US airstrike in Baghdad kills Iran's top general People are seen through thick tear gas after protesters breached the outer wall of the embassy. Hide Caption 16 of 22 Photos: US airstrike in Baghdad kills Iran's top general A picture taken through a broken window shows a vandalized room in the embassy. Hide Caption 17 of 22 Photos: US airstrike in Baghdad kills Iran's top general US soldiers stand guard inside the embassy. Hide Caption 18 of 22 Photos: US airstrike in Baghdad kills Iran's top general Protesters and militia fighters smash the bullet-proof glass of the embassy's windows with blocks of cement after breaching the outer wall. Hide Caption 19 of 22 Photos: US airstrike in Baghdad kills Iran's top general Iraqi security forces stand guard as protesters, including clerics, hold a prayer inside the walls of the embassy. Hide Caption 20 of 22 Photos: US airstrike in Baghdad kills Iran's top general Iraqi security forces stand guard at the entrance of embassy. Hide Caption 21 of 22 Photos: US airstrike in Baghdad kills Iran's top general Mourners carry the coffins of Iranian-backed paramilitary fighters in Najaf, Iraq, on December 31. The fighters were killed in US airstrikes on Sunday that sparked Tuesday's attacks on the US Embassy in Baghdad. Hide Caption 22 of 22

January 4

The Trump administration formally notified Congress about the US drone strike , as required by law. But the administration has yet to publicly explain the legal justification for killing Soleimani, leading Democratic lawmakers to question whether the President had the authority to order the strike without congressional approval.

The lack of evidence provided to lawmakers and the public has fueled skepticism about whether the strike was justified.

The President "has been reluctant to take military action," but the killing of the US contractor late last month, the wounding of others and the protests at the US Embassy in Baghdad "crossed his line," a Republican congressional source familiar with the administration's decision to kill Soleimani told CNN.

Trump vowed specific military action against Iran if it "strikes any Americans, or American assets."

"We have ... targeted 52 Iranian sites (representing the 52 American hostages taken by Iran many years ago), some at a very high level & important to Iran & the Iranian culture" and "if Iran strikes any Americans, or American assets... Iran itself, WILL BE HIT VERY FAST AND VERY HARD," Trump wrote in a series of tweets.

Within the Trump administration, there is widespread opposition to targeting cultural sites in Iran should the US launch retaliatory strikes against Tehran, two senior US officials said.

....hundreds of Iranian protesters. He was already attacking our Embassy, and preparing for additional hits in other locations. Iran has been nothing but problems for many years. Let this serve as a WARNING that if Iran strikes any Americans, or American assets, we have..... — Donald J. Trump (@realDonaldTrump) January 4, 2020

....targeted 52 Iranian sites (representing the 52 American hostages taken by Iran many years ago), some at a very high level & important to Iran & the Iranian culture, and those targets, and Iran itself, WILL BE HIT VERY FAST AND VERY HARD. The USA wants no more threats! — Donald J. Trump (@realDonaldTrump) January 4, 2020

January 5

Thousands flood the streets to mourn Iranian Gen. Qasem Soleimani and others killed in the Friday drone attack.

Soleimani's body arrived in his home country, where thousands mourned him.

Meanwhile, Maj. Gen. Hossein Dehghan, the military adviser to Iran's Supreme Leader, told CNN in an exclusive interview that Tehran's response will "for sure be military." Iran would retaliate directly against US "military sites," Dehghan said in the most specific and direct threat yet by a senior Iranian official following the killing.

In the United States, Secretary of State Mike Pompeo backed Trump's strong threat to Iran . "The American people should know that we will not waver," he said.

The fallout continued in Iraq and Iran.

In Baghdad, parliament voted for the government to work on a plan to end the presence of US troops in Iraq. Trump on Sunday threatened sanctions on Iraq if US troops are expelled.