When Russia provided military support to separatists in Ukraine, columns of Russian tanks were instrumental in turning back Ukrainian Army offensives and seizing government strongpoints, notably the Donetsk International Airport in January 2015. For hawks like Senator John McCain pushing for the United States to provide direct military aid to Ukraine, Javelin missiles were cited as a key weapon system that might have reversed the Ukrainian Army’s fortunes on the battlefield—and one far more practical to put into action than a main battle tank or jet fighter.

The U.S.-made FGM-148 Javelin is one of the premier portable anti-tank missile systems in the world. It’s also an expensive piece of kit, with each missile typically costing more than the targets it eliminates.

Still, the infrared guided Javelin has proven itself in combat in Iraq, Afghanistan, and Syria and has reliable shtick that should work on virtually any tank out there—it hits them on the weak top armor. It’s also exposes its crew to less danger than the typical guided missile system. Because it’s such a lightweight system, it may end up being a first responder on the ground to emergencies that could be described as “massive, unexpected tank invasions”—a scenario the U.S. military could have faced during Operation Desert Shield, when it deployed light infantry to defend Saudi Arabia, and currently fears in the Baltics.

The Javelin is so effective that who the United States sells or gives Javelins to has become a political issue on more than one occasion. Within the U.S. military, the Javelin also looks set to transition from being purely an infantry system to being mounted on vehicles.

So How Does One Throw These Anti-Tank Spears (and Why Are They Powerful?)

The Javelin doesn’t look as sleek and deadly as its name would have you think—it resembles a clunky dumbbell slightly over one meter in length. Fortunately, you don’t need good looks to blow up a tank.

The Javelin’s Command Launch Unit—CLU—has a sophisticated infrared sensor with multiple viewing modes, including 4x optical zoom, a 4x green-lit thermal view, and a 12x narrow-vision zoom activated for targeting. The seeker in the missile even provides a fourth 9x thermal viewing mode. The CLU can therefore serve as a handy scanning device for the infantry. The thermal viewers on the Javelin needs to be cooled off to function well, which theoretically takes 30 seconds, but might take a bit longer if you’re in Baghdad and it’s a breezy 120 degrees at noon. The system also incorporates multiple safeguards to avert or abort accidental launch.

The CLU, when loaded with a missile, weighs in at 50 pounds (most of the weight comes from the missile), and can be fired from a crouch or even seated position. That’s a lot lighter than the wire-guided TOW or other long-range missiles that typically required a heavy tripod. Still, it’s not exactly something you’d want to run a marathon with.

Once the firer acquires a target, locks the infrared seeker on to it and pulls the trigger, the Javelin missile is ejected out of the CLU without using its rocket motor in a “soft launch” creating relatively little back blast. Missile launch back blast not only makes it easy for opposing forces to spot the launcher after firing, but can make launching while inside a confined space (a building) a deadly risk. So the Javelin’s small backblast is very handy for keeping the operator alive. Still, the launch does blow back some gas, so you don’t want to stand directly behind it.

Afterwards, the Javelin’s gunner must… actually, the gunner could play Candy Crush on their cell phone if they wanted to, because unlike most long-range anti-tank missiles, the Javelin is a fire-and-forget system and requires no further input after lunch. The Javelin crew is free to duck into cover and concealment, rather than being forced to remain fixed in place guiding the missile towards the target, as is necessary with Semi-Automatic Command Line-Of-Sight (SACLOS) systems such as the wire-guided TOW or laser-guided AT-14 Kornet.

After launch, a Javelin shoots forward horizontally for a second before its rocket motor ignites and it climbs up 150 meters into the air, known as a “curveball” shot. It’s quite a sight, as you can see in this video.

The missile’s infrared seeker, benefiting from gyroscopes and gimbels, makes adjustments using thrusters to ensure its trajectory leads it to plunge almost vertically onto the infrared signature it was locked onto.

A Javelin fired in this manner will strike the top armor of an armored vehicle, which is generally much thinner than the frontal or even side armor. The Javelin’s 127 millimeter shaped charge warhead is estimated to penetrate the equivalent of 600 to 800 millimeters of Rolled Hardened Armor (RHA), which is not particularly impressive, given that modern tanks now feature composite armor that is extra effective against such warheads. But that doesn’t really matter: it’s still more than enough to penetrate the top armor of anything out there—at least, as long as we don’t consider other defensive system.

One common defense which sometimes does reinforce top armor is explosive-reactive armor (ERA), a layer of explosive bricks covering a tank intended to prematurely detonate the shaped charges used by missiles.

However, the Javelin has a tandem charge warhead designed to defeat ERA using a ‘precursor’ charge at the front of the warhead to take out the local ERA brick, blasting open a gap through which the main warhead can hit the tank’s conventional armor.

The Javelin can also be fired in direct attack mode, useful for hitting targets that are too close for the top attack, or that benefit from top cover, like a bunker or cave entrance. The direct-fire mode could also be effective against low flying helicopters.

One of the Javelin’s few limitations is its range—2.5 kilometers. Though adequate for most combat situations, older missiles like the TOW or Kornet boast ranges of 5 kilometers or more.

Russia is also aware of the Javelin’s capabilities—and their latest tanks feature several countermeasures intended to defeat them. New Relikt and Mechanit ERA systems feature dual layers of radar-triggered ERA plates designed to defeat tandem charge warheads. The Shtora and the newer Afganit Active Protection Systems can also deploy ‘soft kill’ multi-spectral grenades and flares designed to obscure the tank from infrared seekers or divert them to other heat sources.

However, the latest infrared sensors have also improved in their ability to see through obscuring haze and distinguish flares from the original target. And “hard-kill” active defenses designed to shoot incoming missiles down would need to be able to shoot vertically above the tank to tackle a top-attack Javelin—which the new Afganit system on the T-14 tank, with launch tubes nestled at a horizontal angle under the turret, doesn’t seem capable of doing.

So would Relikt-style ERA and soft-kill infrared defenses work against the Javelin? There’s simply no way to know for sure, unless Moscow were suddenly to invite Washington to test its anti-tank missiles against its best tanks in a friendly competition. But given that relations are too frosty for the United States to participate in Russia’s annual tank biathlon, don’t count on that happening.

So Do They Actually Work?

The Javelin was designed in the 70s and 80s, when the leaders of the U.S. military had nightmares about being overrun by endless hordes of Soviet tanks—a fear worsened by the generally poor performance of the M47 Dragon missile in use at the time.

However, the Javelin finally entered service with the U.S. military in 1996 after the Cold War had ended, and first saw action in 2003 during the U.S. invasion of Iraq.

At the time, the United States was not able to deploy troops in Northern Iraq by land, so it instead air dropped Special Forces and paratroopers that fought alongside Kurdish peshmerga fighters. In the Battle of Debecka Pass, a force of a few dozen Special Forces operators and a larger peshmerga contingent engaged and destroyed an Iraqi mechanized company of over a hundred soldiers. The U.S. force had just 4 Javelin launch units. Nineteen Javelins missiles were fired, seventeen of which hit, destroying two T-55 tanks, eight MT-LB armored personnel carriers, and several trucks. Reportedly, all of the Javelins shots were made at 2,200 meters range or further—close to or exceeding the official maximum range of the weapon—and one hit was even reported at 4,200 meters.

Javelins knocked out several more tanks during the Iraq War, including Type 69 tanks and Lion of Babylon T-72s, none of them cutting edge types. As the conventional phase of the conflict ended, the Javelins main duty soon came to ‘sniping’ smaller, softer targets. The Javelin’s precise targeting scope was ideal for spotting and taking out at long ranges insurgent heavy weapons teams armed with machine guns, missiles, or recoilless rifles, as well as the occasional pickup truck. Other weapons systems available to the infantry lacked the combination of long range and precision.

The irony of using Javelins to destroy pickup trucks and machine guns is that the roughly $80,000 Javelin missiles cost considerably more than the weapon systems they are destroying. This has reportedly has led U.S. forces to at times hold back on using the weapon in Afghanistan. Though considered a ‘lighter’ weapon than the vehicle-mounted TOW missile, significantly larger numbers of TOW missiles have been expended since 2003.