WASHINGTON — The Pentagon’s most recent package of weapons for Ukraine includes relics from the Cold War to help blunt Russian advances and limit their ability to maneuver during an expected spring offensive.
Those weapons, M21 anti-tank land mines, have been in service with the Defense Department since at least the early 1960s. An unknown number of them will be sent to Ukraine as part of a $325 million package of aid from U.S. military stockpiles that was announced this week, the 36th such transfer of lethal matériel to Kyiv since August 2021.
M21 mines — large metal-bodied weapons that are usually buried and explode when a vehicle drives over them — contain a specialized warhead built to punch through inches of armor plating.
“Anti-tank land mines are an important defensive capability against Russia’s tanks and armored vehicles, helping Ukraine’s forces repel Russia’s attacks and shape the battlefield to Ukraine’s advantage,” Maj. Charlie Dietz, a Pentagon spokesman, said in a statement on Thursday.
The decision to provide M21s appears to carefully thread the needle between various areas of concern, given the controversy that has accompanied the use of land mines for decades.
One issue is legality. As an anti-tank weapon, the M21 is not banned by the 1997 Ottawa Convention — an international treaty signed by 133 nations that prohibits the stockpiling and use of anti-personnel mines, which are usually much smaller and kill or maim people who step on them.
By comparison, anti-tank mines typically require a couple hundred pounds or more of pressure to detonate, such as from a truck or tank. Unlike some models of American-made anti-tank mines, the M21 cannot be fitted with any secondary fuzes that would allow booby-trap devices to be added, which also keeps it from potentially running afoul of certain provisions of the treaty.
Ukraine is a signatory to the Ottawa Convention, while the United States and Russia are not. The Biden administration has said, however, that it would use anti-personnel mines only in the defense of South Korea.
Another issue involves post-conflict concerns: whether the weapons can be easily located with metal detectors and ground-penetrating radars, and how long they remain lethal once planted.
Although the U.S. military developed anti-tank land mines during the Cold War built mostly of plastic to make them hard to detect, the M21 is metal and would be comparatively much easier to find when mine clearance efforts begin.
The latter concern, however, remains unaddressed: Like mines of its era, the M21 has no self-destruct feature. So Ukrainian troops will probably be expected to carefully map where they place the mines for later clearance operations.
According to a 2002 report from the General Accounting Office, now known as the Government Accountability Office, the Pentagon had more than 178,000 M21 mines stockpiled at the time. The report says that the U.S. military last used anti-tank mines during Operation Desert Storm in 1991, though not the M21.
The M21 is considered a “heavy mine” at about nine inches in diameter and eight inches high, and weighing 17 and a half pounds. When triggered by a downward force of nearly 300 pounds, the mine explodes, throwing a curved steel plate upward into the targeted vehicle’s hull, wheels or tracks.
A U.S. Army technical manual notes that the M21 can penetrate a three-inch armor plate at a distance of 21 inches.
The M21 is the second type of anti-tank land mine the United States has provided to Kyiv.
In September, the Pentagon announced it would send 1,000 155-millimeter artillery shells it calls RAAMS, for Remote Anti-Armor Mine System, which are fired from howitzers and create temporary minefields among enemy forces.
The shells break open midair and release nine small puck-like munitions that fall to the ground unguided, with each containing about one and a quarter pound of high explosives.
Each small mine contains a magnetic sensor that causes it to explode when a vehicle approaches. There are two versions: one meant to self-destruct after four hours, the other after 48 hours.
The most recent data available shows that the Pentagon had sent 14,000 of the shells to Ukraine as of April 4.
Ukraine’s army has long used Soviet-era TM-62 anti-tank mines in its war with Russia, as have the Russian invaders. Whether the provision of M21s signals that Ukraine’s stock of TM-62s is running low, or that the M21 is needed for other reasons, is unclear.