• Tensions between the US and Iran have reached historic heights in recent months, prompting fears of a new war in the Middle East among lawmakers in Washington.
  • The US and Iran are locked in a tit-for-tat stalemate as they both seek to gain leverage over the other in a broader dispute linked to the 2015 nuclear deal and US President Donald Trump's decision to withdraw the US from it.
  • On the evening of January 2, the Pentagon confirmed that the US military, acting on the orders of the president, killed top Iranian general Qasem Soleimani.
  • Soleimani is the highest profile official on either side to be killed in the ongoing tensions.
  • Visit Business Insider's homepage for more stories.

Rising tensions between the US and Iran have sparked fears of a military confrontation and potentially an all-out war.

Here's a timeline of the evolving situation, and a summary of what both countries have been saying.

In May 2018, President Donald Trump withdrew the US from the 2015 Iran nuclear deal. Tensions between the US and Iran have risen ever since and reached a boiling point in recent weeks — particularly after the US in April moved to block all countries from buying Iranian oil.


On May 5, National Security Adviser John Bolton released a statement announcing the US was deploying an aircraft carrier strike group and B-52 bombers to the Middle East to counter threats from Iran.

Source: WhiteHouse.gov

Bolton said that the deployment was designed to send "a clear and unmistakable message to the Iranian regime that any attack" on the US or its allies "will be met with unrelenting force." Bolton added, "The United States is not seeking war with the Iranian regime, but we are fully prepared to respond to any attack."

The USS Abraham Lincoln carrier strike group, which consists of the carrier and its powerful carrier air wing, as well as one cruiser and four destroyers, moved into the region earlier this month along with a number of B-52 Stratofortress heavy long-range bombers.


A US official said the show of force was in response to "clear indications" of a "possible attack" against US forces in the region by Iran or its proxies.


Acting Defence Secretary Patrick Shanahan characterised the deployment as a "prudent repositioning of assets in response to indications of a credible threat by Iranian regime forces."

On May 8, US Air Forces Central Command announced that F-15C Eagle fighter jets were repositioned within the region to "defend US forces and interests in the region." The next day, the Pentagon announced that the USS Arlington, an amphibious landing ship, and a Patriot surface-to-air missile battery were also on their way.

Source: US Air Forces Central Command

Democratic lawmakers have raised alarm bells over these developments. Sen. Chris Murphy, for example, on May 7 tweeted, "Hey everybody, we are at war in 3 different countries — Iraq, Afghanistan, and Syria — and inching toward conflict in 2 more — Venezuela and Iran."


Fears from Democratic lawmakers of a war with Iran are largely linked to their wariness toward Bolton, who's long been hawkish toward Iran and has called for military strikes against it before. Bolton was also one of the architects of the ultimately disastrous US invasion of Iraq in 2003.


Republican lawmakers like Sen. Marco Rubio have rejected the idea the US wants a war with Iran, but he also said "any efforts by Iran to threaten shipping in the Strait of Hormuz and/or to target U.S. naval vessels or commercial shipping vessels will result in a swift, devastating & justified response."


Amid all of this, Iranian President Hassan Rouhani on May 8 threatened to partially withdraw from portions of the 2015 nuclear deal.


The same day, the Trump administration announced new sanctions against Iran targeting its metal exports.

Source: The Washington Post

"We have information that you don’t want to know about,” President Donald Trump said on May 9 in response to questions on the move. “They were very threatening and we have to have great security for this country and many other places.” He also urged Iran to hold talks with him regarding its nuclear program.

Source: Reuters

On May 10, Ayatollah Tabatabai-Nejad, a high-ranking cleric in the Iranian government, warned that US forces will face "dozens of missiles" if any move is made against Iran. The next day, Yadollah Javani, the deputy head of political affairs of Iran's Islamic Revolutionary Guards Corps, said that the US "wouldn't dare to launch military action against us."


Overall, Trump has been fairly vague in responding to questions about Iran. "We'll see what happens with Iran. If they do anything it'll be a very bad mistake, if they do anything," Trump said on May 13, adding, "If they do anything, they will suffer greatly."


Meanwhile, reports have also emerged suggesting the Trump administration has discussed a plan to send 120,000 troops to the Middle East if Iran attacks US forces in the region or makes significant steps toward developing nuclear weapons.


Trump on May 14 rejected these reports but also said he's prepared to send "a hell of a lot more" troops than 120,000 if necessary.


Iranian Supreme Leader Ayatollah Ali Khamenei on May 14 said his country would not go to war with the US. But in what was perhaps a veiled threat, he also signaled that it wouldn't be hard for Iran to enrich uranium to weapons-grade levels.


On May 14, Yemen's Iran-backed Houthi rebels carried out drone attacks on Saudi oil facilities. The kingdom of Saudi Arabia is a close ally of the US, which has supported the Saudi-led coalition in the war against the Houthis in Yemen. With that said, it's not clear if these attacks were linked to rising tensions between the US and Iran.

Source: The New York Times

Sen. Bernie Sanders, one of the top contenders for the 2020 Democratic nomination, on May 14 said, "It appears that John Bolton wants a war in Iran. A war in Iran would, in my view, be many times worse than the Iraq War." Sanders said he's "working hard" to ensure that if Trump wants to take military action against Iran he must seek congressional authorization.

Source: CBS News

The US on May 15 ordered all nonessential government staff to leave Iraq. The State Department didn't fully explain the move, but it's viewed as a possible response to the increasingly tense situation between Washington and Tehran. This also came roughly a week after Secretary of State Mike Pompeo made an unscheduled visit to Iraq.

Source: CNN; The New York Times

Major General Hossein Salami, the commander of Iran's elite Islamic Revolutionary Guards Corps, on May 15 said, "We are on the cusp of a full-scale confrontation with the enemy." Salami added, "This moment in history, because the enemy has stepped into the field of confrontation with us with all the possible capacity, is the most decisive moment of the Islamic revolution."


The Trump administration has taken a hardline stance against Iran from the beginning, and defied US allies by withdrawing from the Iran nuclear deal. In keeping with this stance, Trump recently designated Iran’s Revolutionary Guard Corps a foreign terror group.


Trump on May 19 issued a grave threat to Iran, tweeting, "If Iran wants to fight, that will be the official end of Iran. Never threaten the United States again!"


Iranian Foreign Minister Javad Zarif responded to Trump's threat via Twitter the next day. He said Trump "hopes to achieve what Alexander, Genghis & other aggressors failed to do," adding, "Iranians have stood tall for millennia while aggressors all gone." Zarif said "economic terrorism" and "genocidal taunts" won't "end Iran."

Source: Twitter

Trump on May 24 announced the US is sending 1,500 additional troops to Iran and said they will serve a "mostly protective" role.


Two oil tankers were attacked on June 13 in the Gulf of Oman. The Trump administration has blamed Iran, which has denied any responsibility. Some US allies are skeptical of the Trump administration's claims and want an independent probe.


Iran on June 17 announced it would violate the 2015 nuclear deal by the end of the month via ramping up its enrichment of low-grade uranium and increasing its uranium stockpile.

After Iran's announcement on the nuclear deal, the Pentagon said it's deploying an additional 1,000 troops to the Middle East.

On June 20, Iran shot down a US Navy drone. The Iranian government claims the drone entered its airspace, but the US rejects this and said the drone was flying in international airspace and never entered Iranian territory.


After the drone incident, Trump almost launched in retaliatory military strike against Iran, but pulled back at the last-minute. He cited concerns about civilian casualties.


Trump on June 24 announced new "hard-hitting" sanctions against Iran. "Today's actions follow a series of aggressive behaviors by the Iranian regime in recent weeks, including shooting down of US drones," the president said at the time.


Iran on July 1 announced it's violating the 2015 nuclear deal by breaching the cap on its uranium stockpile of 300 kg (660 pounds). It also threatened to enrich uranium to weapons-grade levels by July 7 if it doesn't get sanctions relief.


In a statement responding to Iran's announcement, White House press secretary Stephanie Grisham on July 1 said, "The Iranian regime took action today to increase its uranium enrichment. It was a mistake under the Iran nuclear deal to allow Iran to enrich uranium at any level...Maximum pressure on the Iranian regime will continue until its leaders alter their course of action. The regime must end its nuclear ambitions and its malign behavior."

Iran on July 8 announced it had surpassed the 2015 nuclear deal's cap on uranium enrichment levels (3.67%). It began enriching uranium up to levels of 4.5%, which is still far below the level needed to produce a nuclear weapon (90%).

Source: IAEA

Trump on July 18 announced the USS Boxer had shot down an Iranian drone in the Strait of Hormuz. The president said the drone threatened the US ship. "The drone was immediately destroyed," Trump said. "This is the latest of many provocative and hostile actions by Iran against vessels operating in international waters."

Iran on July 19 seized a British-flagged oil tanker, the Stena Impero. Iranian state media said the British tanker Stena Impero was seized by the Islamic Revolutionary Guard Corps. The incident increased tensions between Iran and the West.

Source: Insider

In late July, the Trump administration announced it's hitting Iranian Foreign Minister Javad Zarif with sanctions, making the prospect of a diplomatic solution to hostilities between the US and Iran even less likely.

Source: Insider

Iranian President Hassan Rouhani on September 4 announced Iran would begin developing more advanced centrifuges in what represented its third step away from the 2015 nuclear deal.

Source: Insider

Over the course of September, Trump and Rouhani at times flirted with the idea of holding talks at the United Nations General Assembly. But Iran's Supreme Leader Ali Khamenei has said no such talks can be held unless the US lifts sanctions and returns to the 2015 nuclear deal.

On September 10, Trump dismissed John Bolton as national security adviser. After, Rouhani adviser Hesameddin Ashena tweeted that Bolton's ousting is a "decisive sign of the failure of the U.S. maximum pressure strategy in the face of the constructive resistance from Iran."

Source: Insider

On September 14, two major oil facilities in Saudi Arabia were attacked, disrupting the global oil supply. Iran-backed Houthi rebels claimed responsibility, but the Trump administration blamed Iran.

In the immediate aftermath of the attack, Trump tweeted that the US was "locked and loaded," which signaled there might be a military response. In the days that followed, Trump walked this back slightly saying he did not want war. Meanwhile, the Trump administration announced new sanctions against Iran.

On September 19, Zarif warned that if the US or Saudi Arabia attacked Iran it would lead to "all-out war." He added, "We won't blink to defend our territory." This came a day after Pompeo called the attack on the Saudi oil fields an "act of war."

Source: CNN

Iran in early November announced it was taking a fourth step away from the 2015 nuclear deal — injecting uranium gas into 1,044 centrifuges that had been kept empty under the terms of the agreement.

Source: Insider

A rocket attack on December 27 killed a US contractor and injured four US service members at a base in Kirkuk, which is in the northeastern part of Iraq. The US has blamed the deadly attack on Kataeb Hezbollah, an Iran-backed militia. The US retaliated with airstrikes that killed dozens of the militia's fighters. Subsequently, the US embassy in Baghdad was consumed by violent protests, prompting the US to send about 100 more Marines to the embassy for protection.

Source: Insider

Trump explicitly blamed Iran for the violent protests at the embassy, and threatened Tehran in a Dec. 31 tweet: "Iran will be held fully responsible for lives lost, or damage incurred, at any of our facilities. They will pay a very BIG PRICE! This is not a Warning, it is a Threat. Happy New Year!"

On the morning of January 2, Defense Secretary Mark Esper warned the US might conduct preemptive strikes on Iranian-backed militias. Esper said: "If we get word of attacks, we will take preemptive action as well to protect American forces, protect American lives. The game has changed."

Source: Politico

On the evening of January 2, the Pentagon confirmed that the US military, acting on the orders of the president, killed top Iranian general Qasem Soleimani. "The US military has taken decisive defensive action to protect US personnel abroad by killing Qasem Soleimani, the head of the Iranian Revolutionary Guard Corps-Quds Force," the Pentagon said in a statement.

Soleimani is the most high profile official on either side to be killed in the ongoing tensions between the US and Iran.

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