The U.S. drone strike that killed Iranian Gen. Qassem Soleimani and Iraqi paramilitary commander Abu Mahdi al-Muhandis on January 2, 2020, seemed to many Americans like the start of a war.

Iranian officials vowed enteqâm-e sakht, "hard revenge." President Donald Trump in turn threatened to bomb Iranian cultural sites in response to any retaliation. On January 7, Iran called his bluff, firing over a dozen ballistic missiles at U.S. forces in Iraq. Fortunately, no Americans were killed, and Trump refrained from further military action.

Unbeknownst to many Americans, we've been hurtling toward a worsened conflict with Iran for nearly two years now. The Trump administration has been quietly escalating against the country and its allies using a selection of counterterrorism laws, many of them passed after 9/11, that allowed it to act without going through Congress or the public. Former President Barack Obama, meanwhile, left a force in the region to counter the Islamic State that the Trump administration eventually pointed against the Islamic Republic.

Trump and his advisors objected to the violence carried out by Iran and its proxies across the Middle East. They also disliked Obama's "nuclear deal," which lifted U.S. economic sanctions on Iran in order to get international inspectors access to the country's nuclear research program. So in 2018, the Trump administration replaced Obama's deal with a campaign of sanctions aimed at forcing the Iranian government to change a range of foreign and domestic policies.

Obama had waived many Iran sanctions previously passed by Congress, meaning Trump could simply allow the waivers to expire. But he also used a curious legal tool to maximize the pressure: Section 219 of the Immigration and Nationality Act, which allowed Secretary of State Mike Pompeo to designate the Islamic Revolutionary Guard Corps (IRGC), a branch of the Iranian military, as a foreign terrorist organization in April 2019.

The U.S. government had never used Section 219 to declare the army of a sovereign state a terrorist group. The Trump administration then used the designation to put sanctions on Iran's oil, banking, construction, and steel industries.

"The IRGC is very expert at creating front companies disguised as any number of organizations, including humanitarian organizations," claimed Brian Hook, the State Department official in charge of Iran. "You can never know if you're supporting commerce or terrorism."

In May 2019, the Trump administration took a further step: By slapping buyers of Iranian oil with economic sanctions, it hoped to cut exports to zero. Iran had threatened to retaliate for such a move by disrupting the global trade in foreign oil. Soon thereafter, tankers began to explode off the country's coast.

U.S. officials blamed Iranian sabotage, and U.S. naval forces massed in the Persian Gulf. On June 20, tensions nearly boiled over when Iran shot down a U.S. surveillance drone. Trump reportedly came within minutes of launching airstrikes against the country before suddenly changing his mind.

Meanwhile, the Trump administration was sitting on a massive legal and military apparatus originally designed to crush the Islamic State, an apocalyptic cult rampaging across Iraq and Syria. That apparatus was created when Obama launched Operation Inherent Resolve in 2014, using his powers as commander in chief under Article II of the Constitution.

It's debatable how far these Article II powers stretch. At the very least, they include self-defense. In the most expansive interpretation, they allow the president to take almost any military action, even without permission from Congress. Trump's State Department told a skeptical Senate Foreign Relations Committee in August 2019 that Article II authorities include the "protection of U.S. persons or property, support of allies, support of U.N. Security Council resolutions, promoting regional stability, [and] deterrence of the use of" weapons of mass destruction.

The Obama and Trump administrations also justified the campaign against the Islamic State, previously known as ISIS, under two authorizations for the use of military force (AUMFs) passed by Congress more than a decade earlier. The 2001 AUMF allowed the president to go after Al Qaeda, of which the Islamic State was a spinoff. The 2002 AUMF, which approved the overthrow of Iraqi President Saddam Hussein, was vague enough to include the Islamic State because it only mentioned "the continuing threat posed by Iraq."

The House of Representatives voted to revoke the two AUMFs in July and December 2019, after the escalations with Iran began, but the amendments were defeated in the Senate.

Only a few thousand Americans were ever deployed as part of Operation Inherent Resolve, the anti–Islamic State coalition, mostly in training and support roles. But the "light footprint" force was stationed along the "Iranian land bridge," a term used in Washington to describe the chain of territories from Iran's border to the Mediterranean coast controlled by pro-Iran factions.

"We actually had to coexist in this environment with Shi'a [Muslim] militia groups that were, again, fighting ISIS, but were being supported by Iran," retired General Joseph Votel, commander of U.S. forces in the Middle East from March 2016 to March 2019, says. "Within the rubric of the Defeat-ISIS campaign, I would not have had any particular military tasks that were related to Iran."

That began to change in September 2018, when National Security Advisor John Bolton declared that U.S. forces would stay in Syria "as long as Iranian troops are outside Iranian borders, and that includes Iranian proxies and militias."

In October 2019, protests against Iranian influence in Iraq broke out, followed by protests against gas prices in Iran. The Iranian government, in a spasm of paranoia, shut down the internet and killed hundreds of protesters in its own country. Iranian-backed militias also massacred Iraqi protesters—and began to act out by firing rockets at U.S. forces in Iraq.

Most of these attacks hurt no one, but on December 27, a rocket killed an American translator named Nawres Hamid in Iraq. Combined Joint Task Force Operation Inherent Resolve responded by killing 25 Iraqi militiamen in a series of air raids.

U.S. military officials called their retaliation "precision defensive strikes" and emphasized the need for "force protection"—that is, protecting the U.S. forces already in Iraq for other reasons. But Iraqi militia supporters responded by ransacking part of the U.S. Embassy in Baghdad on the last day of 2019. In early January, things spun out of control: Soleimani was dead, and Iranian missiles were in the air.

Trump administration officials offered two justifications in the days after the Soleimani assassination. The first was that the general posed some kind of "imminent" threat to U.S. forces in Iraq. Yet General Mark Milley admitted to reporters in the Pentagon that the intelligence did not "exactly say who, what, when, where" the threat was. In addition, the killing appeared to make the Iranian threat worse, as Combined Joint Task Force Operation Inherent Resolve had to suspend all operations against the Islamic State for security reasons soon after.

The second justification was that the 2002 AUMF provided a blank check for any military action in Iraq—an argument Sen. Rand Paul (R–Ky.) called "insulting."

Trump supporters pulled out a third justification during a January 9 debate in Congress: Militias armed by Soleimani were estimated to have killed 608 U.S. troops during the first U.S. occupation of Iraq from 2003 to 2011. But Rep. Elissa Slotkin (D–Mich.), a CIA veteran who served in the country, wasn't buying it. She proposed a resolution to rein in Trump's war powers.

"I have watched friends and colleagues hurt or killed by Iranian rockets, mortars, and explosive devices," Slotkin said. Nonetheless, "Congress has long abdicated its responsibility, as laid out in the Constitution, to our troops when it comes to authorizing war."