A U.S. Army carry team moves the flagged-draped coffins containing the remains of the US soldiers killed in the retaliatory Iranian strike on Kuwait's Port of Shuaiba, in Dover, Delaware, United States on March 7, 2026. U.S. Army Reserve Members Maj. Jeffrey OâBrien, Capt. Cody Khork, Chief Warrant Officer 3 Robert M. Marzan, Sgt. 1st Class Nicole Amor, Sgt. 1st Class Noah Tietjens, and Sgt. Declan Coady, were killed in the retaliatory Iranian strike on Port of Shuaiba, Kuwait. (Photo by Kyle Mazza/Anadolu via Getty Images)

Anadolu via Getty Images

President Donald Trump has said that if post-ceasefire Iranian attacks in the Middle East kill any U.S. troops, that would cross a red line and possibly reignite the war against Tehran. His statement is the latest reminder that, for at least six years now, the U.S. has often avoided escalatory retaliations when Iranian or Iran-allied militias or proxies injured U.S. troops in past attacks.

Speaking to reporters in the Oval Office on Thursday, Trump left open the possibility that he may resume the war with Iran if Tehran kills U.S. troops, stating in response to a question, “Yeah, if they killed U.S. troops, I think I would do that very quickly.”

While Trump appeared to be characteristically talking off the cuff, his answer reflects how the U.S. has, in many cases, dealt with Iranian and Iranian proxy attacks on its troops for at least six years now.

The U.S.-Israeli war with Iran launched on February 28 has been halted since a fragile ceasefire took effect on April 8. While Iranian and militia proxy attacks against U.S. bases and the Arab Gulf allies that host them have intermittently continued since then, none have killed U.S. troops or personnel.

In late May, Kuwaiti air defenses intercepted an Iranian Fateh-110 short-range ballistic missile over Ali Al Salem air base. Falling missile debris resulted in several Americans on that Kuwaiti base suffering minor injuries and two MQ-9 Reaper drones badly damaged, Bloomberg reported on May 30.

Despite that attack taking place during the ceasefire, the U.S. doesn’t appear to have retaliated for that specific incident, most likely due to the fact that the missile was intercepted and the subsequent debris didn’t cause any deaths or serious injuries.

The U.S. has previously chosen not to react to similar incidents since late in the first Trump administration and through the intervening presidency of Joe Biden.

On June 20, 2019, Iran shot down a U.S. RQ-4A Global Hawk surveillance drone over the Strait of Hormuz. Trump initially decided to retaliate but later halted the attack 10 minutes before it began after learning it could kill 150 Iranians, reasonably deeming that “not proportionate to shooting down an unmanned drone.” After all, no American pilot or crew was killed, injured, captured, or even endangered.

The following December, the U.S. would respond quite differently. A December 27 rocket attack targeting U.S. troops at K-1 Air Base in Kirkuk province in Iraq killed an American civilian contractor and injured four U.S. personnel hosted there as part of the U.S.-led anti-Islamic State coalition. The U.S. blamed the Iran-backed Iraqi Kataib Hezbollah militia, which denied responsibility. Two days later, U.S. warplanes unleashed a series of punitive airstrikes against Kataib Hezbollah targets in Iraq and Syria, killing an estimated 25 suspected militants and injuring another 55.

Things did escalate quickly from there. Supporters of the Iran-backed group attacked the U.S. Embassy in Baghdad on December 31. On January 3, Trump ordered the fateful assassination via drone strike of Iran’s powerful Islamic Revolutionary Guard Corps’ extraterritorial Quds Force commander Qasem Soleimani. That strike killed Soleimani while he was traveling by car from Baghdad International Airport with Kataib Hezbollah commander Abu Mahdi al-Muhandis.

An infuriated Iran responded with its first direct attack against U.S. troops a few days later, firing ballistic missiles at Iraq’s western al-Asad airbase. American troops stationed at that base weren’t protected by MIM-104 Patriot missiles or any other effective air defense at the time and lacked adequate bunkers or shelters. While none were killed or badly injured physically, several suffered traumatic brain injuries, for which they were awarded Purple Hearts. Trump didn’t retaliate, a decision likely made easier by the seemingly miraculous lack of fatalities.

The following March, rocket attacks on Camp Taji north of Baghdad, which also hosted U.S.-led coalition troops at the time, killed two U.S. troops and one British troop. The U.S. retaliated with targeted airstrikes at suspected militia weapons depots in Syria and Kataib Hezbollah facilities in Iraq.

Early in Biden’s presidency, U.S. troops endured yet another militia rocket attack. On February 21, 2021, a shadowy militia group hurled rockets into Iraqi Kurdistan’s capital city, Erbil, killing a foreign civilian contractor working on the U.S. base in the city’s international airport. The U.S. conducted airstrikes ten days later targeting Kataib Hezbollah and another Iran-backed group in Syria in a relatively limited retaliation.

The base at Erbil airport once again came under attack, with an explosive drone crashing into the barracks but failing to explode that October. A subsequent attack there in December left a U.S. service member in critical condition and two others injured, prompting the U.S. to execute retaliatory strikes against Kataib Hezbollah targets.

Iraq’s Al-Asad base would also find itself under fire once again that November, with a close-range ballistic missile attack injuring eight U.S. personnel, prompting the U.S. military to scramble an AC-130 to conduct a self-defense strike in the area. In another attack, the following January 20, Iran-backed militants fired several ballistic missiles and rockets, prompting the U.S. to fire more than 15 Patriot missiles in self-defense. Still, several U.S. soldiers suffered injuries in that attack and were evaluated for traumatic brain injuries. Another five U.S. service members and two contractors were later injured in another rocket attack on August 5.

While the U.S. certainly did not sit completely idle during those 170 attacks, it did appear to want to avoid any escalation in its tit-for-tat responses to the ones that injured its service personnel. That changed when the self-styled IRI fighters inflicted their first American fatalities during that campaign.

On January 28, 2024, an explosive drone launched by the militants in Syria hit the Tower 22 facility in northeast Jordan on the Syrian border, killing three U.S. troops asleep in their living quarters and injuring another 47. Washington could not feasibly settle for an improvised self-defense strike in the area or for yet another limited tit-for-tat retaliation. And it didn’t. Beginning February 2, strategic U.S. Air Force Rockwell B-1B Lancers flying directly from the mainland United States participated in airstrikes against 85 suspected militia targets in both Iraq and Syria. The Iran-backed IRI militants paused their attacks in the aftermath of that bombardment.

By mid-February, the Pentagon confirmed that an estimated 186 U.S. troops had been injured or killed since the previous October. The vast majority of these, 130, had endured traumatic brain injuries.

That 2023-4 period could have important lessons for the present moment. Iran and its regional militias may well conclude that they can endure limited retaliatory strikes if they injure U.S. military personnel in attacks like the recent one on Kuwait without reigniting an all-out war. They may also conclude that they can avoid more punitive and less proportionate American strikes provided they don’t kill or critically injure Americans in their attacks. By doing so, they can convey to Tehran, in their propaganda, and to their local constituents that they are still actively shooting at American forces in the region and therefore still in the fight and unbowed.

There’s another possible grey zone they may identify and seek to exploit if they haven’t already. For example, they may continue attacks such as the recent post-ceasefire drone strikes originating from Iraq on Saudi Arabia and the United Arab Emirates. Perhaps more ominously, Iran could well continue its direct attacks on Arab Gulf targets and civilian infrastructure, as was seen in the most recent drone attack on Kuwait International Airport on Wednesday, similarly calculating they mightn’t incur a direct U.S. military response—again, provided they don’t kill American troops, contractors, or civilians.

In other words, Trump on Thursday may have redrawn a red line that Iran and its proxies were already intimately familiar with. For now, they may well explore how they can cause maximum disruption in the region without stepping over it and forcing Trump’s hand.