Iranian air-defenses reportedly accidentally shot down a Ukrainian airliner near Tehran on Monday on the night of Jan. 7, 2020.

The incident, in which all 176 passengers and crew aboard the Kiev-bound Ukraine International Airlines flight perished, occurred as Iranian missiles struck bases housing U.S. forces in Iraq, and Tehran’s own forces were on high alert.

U.S. officials told CNN’s Barbara Starr that two missiles from a Tor self-propelled launcher struck the Boeing 737-800, causing it to fall to the ground in flames. Photos that circulated on social media in the aftermath of the shoot-down depicted wreckage from both the 737 and the missiles that apparently brought it down.

Iranian authorities initially blamed the plane’s crash on a technical malfunction.

The 176 people aboard the plane, including scores of Westerners, are the latest casualties in the escalating conflict between the United States and Iran, the latest phase of which began when U.S. president Donald Trump unilaterally withdrew the United States from the 2015 accord limiting Iran’s nuclear program in exchange for relief from sanctions.

Following Trump’s 2018 pullout, Iran resumed enriching large quantities of uranium that the country could use to build its first nuclear bomb. Following a series of bomb and rocket attacks on commercial ships in the Persian Gulf and Iraqi bases housing U.S. personnel, Trump in January 2020 ordered U.S. Special Operations Command to assassinate Qassem Soleimani, the head of Iran’s Revolutionary Guard Corps militia.

A drone on Jan. 2, 2020 struck Soleimani’s vehicle near Baghdad’s international airport, killing the general and one of his deputies. The Trump administration claimed without evidence that Soleimani was planning an imminent attack on Americans. Iran promptly vowed revenge, and five days late lobbed as many as 16 ballistic missiles at two bases in Iraq. No one died in the rocket barrages.

Iranian defenses were on alert as the rockets impacted. Iranian fighter jets took off for defensive patrols. And air-defense systems including the Tors scanned the sky for American warplanes and missiles.

U.S. forces in fact did not strike Iran that night or in the following days. But the Tor crew outside Tehran apparently mistook the Ukrainian 737 for an enemy plane and opened fire.

Tehran acquired 29 Tor systems starting around 2007. Known to NATO as the SA-15 Gauntlet, the Tor replaced older SA-8 Gecko short-range air-defense systems in the Russian and allied militaries. “Like the SA-8 Gecko, the Tor M1 ... is a fully self-contained package, with a search radar, a monopulse tracking and engagement radar and a magazine of ... guided-missiles,” Air Power Australia analyst Carla Kopp wrote.

“The design aims of the Gauntlet were however broader than those for the Gecko, and not only are low-flying aircraft and helicopters intended targets, but also cruise missiles, standoff missiles and smart bombs during their terminal flight phase.”

In the Russian air-defense network, Tors with their seven-mile range help to protect batteries of long-range S-300 surface-to-air missile systems. “Russian thinking is that S-300PMU/S-400 battery elements such as radars and command posts are to be covered by Gauntlet point-defense systems, intended to engage and destroy guided munitions targeting the S-300PMU/S-400 battery elements,” Kopp explained.

“Eight vertically launched 9K331 SAM rounds are carried in sealed magazines [and] these are vertically ejected before ignition using the cold-launch technique,” Kopp wrote. “Once clear of the [launcher], the canard missiles use nose rocket thrusters to pitch over in the direction of the target and effect the engagement. Reaction time to threats is credited in seconds between track confirmation and launch.”

Since the first Tors appeared in the early 1980s, Russia has developed several new variants of the basic system with improvements to its sensors and missiles.

“The Russians have not disclosed the specific control laws used in this design, but it is known that the missiles are flown in an arcing trajectory and perform a shallow dive against a low-flying target,” Kopp wrote. “This is intended to maximise ground clearance of the missile round and facilitate tracking.”

In the aftermath of the shoot-down, Iran has declined to share with international investigators the 737’s in-flight data-recorder. However, in a recent report in the Wall Street Journal, Tehran might seek outside help but "if we can do it ourselves, we will." 

David Axe serves as Defense Editor of the National Interest. He is the author of the graphic novels  War Fix, War Is Boring and Machete Squad.