Hawks in Washington, particularly on the right, have long pushed for more aggressive US action against Iran, including war with the Middle Eastern power.

While President Donald Trump campaigned on his "America First" talking points, he's taken a hostile approach to Iran over the last few years.

Republican lawmakers almost universally celebrated Trump's decision to assassinate Iranian Maj. Gen. Qassem Soleimani, the country's top military commander.

There are a host of reasons why Iran hawks may have pushed Trump to escalate the conflict — and one consideration might be purely political.

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Hawks in Washington, particularly on the right, have long pushed for more aggressive US action against Iran, including war with the Middle Eastern power.

While President Donald Trump campaigned on his "America First" talking points, slamming the Iraq War as the "worst single mistake" in US history and promising Americans that he'd disentangle the country from seemingly never ending conflicts in the Middle East, he's taken an aggressive approach to Iran over the last three years.

But on Friday, Republican lawmakers almost universally celebrated Trump's decision to assassinate Iranian Maj. Gen. Qassem Soleimani, the country's top military commander, in a move widely viewed as an act of war.

Decades of US-Iranian tension

Iran and the US have been adversaries for decades. The two countries have a complex history that involved a CIA-orchestrated coup in the 1950s, a pro-American puppet monarch who was overthrown in 1979 via the Islamic revolution, and the infamous hostage crisis at the US embassy in Tehran that followed the uprising.

The constant Iranian threats against Israel, America's top ally in the Middle East, and chants of "death to America" in Iranian streets have exacerbated the tensions.

In this picture released by an official website of the office of the Iranian Supreme Leader on Tuesday, June 23, 2015, Supreme Leader Ayatollah Ali Khamenei addresses Iranian top officials in a mosque at his residence in Tehran, Iran. Office of the Iranian Supreme Leader via AP

Washington has long feared what might happen if the Iranian regime developed a nuclear weapon. Iran had made advances towards developing nuclear capabilities by the 2010s, which is why the Obama administration prioritized the nuclear deal and de-escalation. When the pact was finally settled in 2015, it was widely celebrated as a major diplomatic achievement.

Trump — along with the Republican party — was outspoken about his disdain for the 2015 Iran nuclear deal, which he's called "defective at its core," ever since it was negotiated by the Obama administration. And despite strong opposition from European allies and US defense leaders, he unilaterally pulled out of the deal in May 2018.

The controversial move was widely celebrated by Republicans, who'd long believed the deal didn't do enough to prevent Iran from developing nuclear weapons or participating in disruptive conflicts across the region.

But there is an at-times vocal minority of Republican lawmakers who've embraced Trump's isolationist instincts and pressed the president to reject the establishment's hawkish stance on Iran.

Rep. Matt Gaetz, a prominent and outspoken Trump supporter, co-sponsored an amendment to the National Defense Authorization Act in June 2019 that would prevent US funds from being used for military action against Iran without congressional authorization. (But Gaetz supported Trump pulling out from the Iran nuclear deal).

"I am grateful that the president is not eager to lurch into another Middle Eastern regime change, in an endless, unfocused, unconstitutional way," Gaetz told The New York Times in June 2019. "President Trump ran as a very different kind of Republican, someone who wanted to end wars, not start them."

Trump insists he doesn't want war or regime change

Trump's former national security adviser, John Bolton, is an Iran hawk and pushed for the US to bomb the country before Trump brought him into the White House in March 2018.

The president repeatedly described Bolton as more pro-war than him.

"I actually temper John, which is pretty amazing," Trump said of Bolton during a press conference in May 2019.

On Friday, Bolton tweeted "congratulations to all involved" in the strike, which he called a "decisive blow" to Iran and said he hoped it would be "the first step to regime change in Tehran."

In May 2018, Rudy Giuliani — Trump's personal lawyer — said the president is committed to regime change in Iran.

"We have a president who is tough," Giuliani told an audience of activists who oppose the Iranian regime. "We have a president who is as committed to regime change as we are."

But Trump has repeatedly said he's not seeking regime change in Iran. On Friday, he insisted that the strike killing Soleimani was designed to prevent, not provoke, war and again insisted he's not seeking the overthrow of the Iranian government.

"Suleimani was plotting imminent and sinister attacks on American diplomats and military personnel, but we caught him in the act and terminated him," Trump said. "We took action last night to stop a war, we did not take action to start a war."

Despite pushing for increased aggression on the US's part, many Republican lawmakers have insisted over the last few years that war with Iran isn't likely.

"You're always concerned about it if it escalates. But I really don't see that. The president is trying to get us out of every armed conflict we're in. I can't imagine him escalating into a new one," said GOP Sen. Shelley Moore Capito told Politico in May 2019.

The reaction among US lawmakers to the assassination of Soleimani was predictably partisan. While Democrats condemned Trump for not seeking congressional authorization and escalating tensions with Iran, Republicans largely praised the president for taking what they described as "decisive" action.

There were a few exceptions on the Republican side on Friday.

"If we are to go to war w/ Iran the Constitution dictates that we declare war," GOP Sen. Rand Paul, long a non-interventionist, tweeted Friday. "A war without a Congressional declaration is a recipe for feckless intermittent eruptions of violence w/ no clear mission for our soldiers. Our young men and women in the armed services deserve better."

Secretary of State Mike Pompeo speaks during a news conference with Chinese State Councilor and Foreign Minister Wang Yi at the State Department. AP/Andrew Harnik

Trump sees potential political gain from war with Iran

There are a host of reasons why Iran hawks may have pushed Trump to escalate the conflict — and one consideration might be purely political.

Notably, Trump repeatedly argued that former President Barack Obama was planning to go to war with Iran in 2011 and 2012 in order to boost his approval ratings and win reelection.

"He's weak, and he's ineffective," Trump said of Obama in 2011. "So I believe that he will attack Iran sometime prior to the election, because he thinks that's the only way he can get elected."

The prediction, which didn't materialize, suggest Trump once believed war with Iran has the potential to help him politically in an election year. (This election year he is facing dismal polling and looming impeachment trial.)

John Haltiwanger contributed to this story.