Here's What You Need to Know: The missiles had first been used in conflict during the Iran-Iraq War, when Iranian Scuds, purchased from Libya, were used against Iraqi cities. Iraq, unable to hit back at distant Iranian cities with its own Scuds, began a program to develop longer-range missiles.

One of the most infamous missiles of the modern era, the Scud short-range ballistic missile was developed as a nuclear asset for Soviet commanders during the Cold War. Today, more than six decades later, the Scud’s DNA has been scattered worldwide, found in ballistic missiles from North Korea to Iran. The lumbering Scud is more visible than ever, with dozens fired in the ongoing Yemeni civil war.

The Scud missile is a direct product of captured wartime German missile technology. Soviet experiments with the Nazi-developed V-2 missile led to a ten-year development effort that culminated in the R-11M missile paraded through Red Square in November 1957. The R-11M was a liquid-fueled missile that rode on a tracked transporter erector launcher not dissimilar to North Korea’s Pukkuksong-2 tracked launcher. The R-11M could launch a conventional high-explosive warhead up to 167 miles and a heavier nuclear warhead up to ninety-three miles. The R-11M was eventually nicknamed “Scud” by NATO, and as subsequent versions emerged became known as Scud-A.

The Scud-A’s short range made it a tactical nuclear delivery system. The missile had poor accuracy, with a circular error probable—or the distance within which half of a missile’s warheads will fall—of 1.8 miles. This, and the primitive state of early nuclear-weapons development, meant that the Scud, despite being a tactical system, was still equipped with large warheads with a yield of twenty to a hundred kilotons.

The basic Scud design was updated several times during the Cold War. The R-17, also known as the Scud-B, was introduced in 1965. Scud-B moved to an 8×8 wheeled tracked erector launcher and a nuclear-payload range increase to from ninety-three to 167 miles. A new inertial guidance system shrank the -B model’s accuracy down to .6 miles, and while the new missile was by no means a “precision-guided weapon,” it was still exponentially more accurate.

Military analyst Steven Zaloga puts the total number of Scuds of all types at about ten thousand, with five thousand to six thousand remaining by 1997. Total launch-vehicle production was estimated at eight hundred. The Scud is out of production, and no longer in service with the Russian military.

The end of the Cold War did not mean the end of the Scud. The missiles had first been used in conflict during the Iran-Iraq War, when Iranian Scuds, purchased from Libya, were used against Iraqi cities. Iraq, unable to hit back at distant Iranian cities with its own Scuds, began a program to develop longer-range missiles. This resulted in the Al Hussein, a ballistic missile with a range of up to four hundred miles. Hundreds of Iranian Scuds and Iraqi Al Husseins were launched during the war, primarily at civilian targets, with Iraq alone firing 516 Scud-Bs and Al Hussein missiles at Iranian territory.

Iraq again used Al Hussein missiles again in 1991, launching an estimated ninety-three of them against Israel and Saudi Arabia during the Persian Gulf War. While the Iraq of Saddam Hussein no longer exists, Iran has continued developing ballistic missiles. The Nuclear Threat Initiative believes Iran has at least two hundred to three hundred Scud-type missiles, with twelve to eighteen mobile launchers, and twenty-five to a hundred Shahab-3 missiles identical to the North Korean Nodong medium-range ballistic missile, with six launchers. The Nodong, as we’ll cover later, is also a descendant of the Scud. NTI, which provided the numbers, warns, however, that those numbers reflect missiles imported from abroad and “do not account for Iranian domestic production.”

Meanwhile, Iran has managed to increase the range of the Shahab-3, resulting in the thousand-mile-capable Ghadr-1. The Ghadr-1 is also stage one of Iran’s Safir space launch vehicle. Recent Iranian progress in solid-fuel missiles has led the country to discontinue further development of Scud-based weapons, but Scuds were undoubtedly instrumental in giving regimes such as Iran a reliable platform for early research and development.

Another major user and developer of the Scud platform is North Korea. Pyongyang received two Scud-Bs from Egypt sometime between 1976 and 1981. The country’s budding missile-research enterprise went to work and by 1986 had developed a homemade copy, the Hwasong-5, with a 10 to 15 percent increase in range and payload.

A requirement to hit U.S. bases in Japan sent North Korean rocket scientists back to the drawing board, and by 1994 they had developed what became known as the Nodong. Nodong has a range of 932 miles, or enough to strike as far as Okinawa. Nodong is not an accurate missile: it has a circular error probable of 1.26 miles. Nodong technology was exported to Iran to create the Shahab-3. Nodongs were also used as the basis for the Taepodong-1 intermediate-range ballistic missile (no longer in service) and a combination of Nodong and Scud engines power the Unha-3 space launch vehicle.

Several Scud-based missiles have been launched during the ongoing Yemeni civil war. The missiles, taken from Yemeni Army stocks, were allegedly sold to the country by North Korea. These missiles have been launched at targets that include the Saudi capital of Riyadh as well as Mecca. A solid estimate of the number of ballistic missiles that have been fired in the conflict is hard to come by. One clue lies in a statement made earlier this year by Raytheon, manufacturer of the Patriot missile, claiming that since “January of 2015, Patriot has intercepted more than 100 ballistic missiles in combat operations around the world.”

The Scud missile, while never firing a shot in anger in the Cold War it was designed for, ironically went on to become a major military threat of the post–Cold War era. The missile has since spawned more dangerous missiles—and even worse, missile research programs—in the hands of rogue states. While the Scud itself will eventually go away, its legacy will continue to haunt the world for decades to come.

Kyle Mizokami is a defense and national-security writer based in San Francisco who has appeared in the Diplomat, Foreign Policy, War is Boring and the Daily Beast. In 2009 he cofounded the defense and security blog Japan Security Watch. You can follow him on Twitter: @KyleMizokami.

This article first appeared in June 2017.

Image: Reuters.