For 58 years, American soldiers have thrown the same grenade into battle. The M67 fragmentation grenade — a baseball-shaped, steel-bodied weapon loaded with 6.5 ounces of Composition B explosive — has traveled with U.S. forces from the jungles of Vietnam to the streets of Fallujah, from the mountains of Afghanistan to every conflict in between. As of this month, it finally has a partner. The U.S. Army has cleared the M111 Offensive Hand Grenade for Full Material Release, the first new lethal hand grenade to enter American military service since 1968. It doesn't use shrapnel. It uses sound.
What Changed, and Why Now
The M111 was developed at Picatinny Arsenal in New Jersey by the Capabilities Program Executive Ammunition and Energetics (CPE A&E), in conjunction with the U.S. Army Combat Capabilities Development Command (DEVCOM) Armaments Center, according to the official U.S. Army press release announcing the Full Material Release. The weapon formally replaces the Mk3A2 offensive hand grenade, which entered service alongside the M67 in 1968 but was pulled from use in the 1970s after its asbestos body was found to cause cancer in the soldiers who carried it.
That withdrawal left the Army without an offensive grenade option for more than four decades. The M67 filled every role, even roles it wasn't designed to fill. The problem became impossible to ignore after the wars in Iraq and Afghanistan.
"One of the key lessons learned from the door-to-door urban fighting in Iraq was the M67 grenade wasn't always the right tool for the job," said Col. Vince Morris, Project Manager for Close Combat Systems at CPE A&E, in the Army's official statement. "The risk of fratricide on the other side of the wall was too high."
The M67's design is optimized for open terrain. When it detonates, its steel body generates lethal fragments that radiate outward in all directions. That's effective when enemies are in the open and friendlies have cover. It becomes a liability inside a building, where fragments deflect unpredictably off walls, floors, and furniture — and where the thin barriers separating rooms offer almost no protection from flying steel.
How Blast Overpressure Kills
The M111 operates on an entirely different principle: blast overpressure, or BOP. When the M111 detonates, it generates a rapid, violent pressure wave that radiates outward from the explosion. Unlike shrapnel, this wave cannot be stopped by interior walls, furniture, or appliances — it moves through enclosed space and finds its targets regardless of cover.
According to an Army fact sheet cited by CNN, the physical mechanism is brutal: "When the high-pressure wave encounters someone, it violently compresses and decompresses tissue. The eardrums, lungs, eyes and gastrointestinal tract are most at risk of rupture and serious damage from smaller blasts." Larger blast waves, the fact sheet continues, can damage the brain or even amputate limbs.
The grenade's plastic body is fully consumed during detonation, eliminating the asbestos hazard that retired its predecessor and generating no shrapnel. The weapon is powered by RDX, an explosive material with a long history in U.S. military munitions. According to the Army's official release, the M111's blast overpressure effects "are less affected by obstacles in enclosed and restricted terrain" compared to fragmentation weapons — meaning a soldier can throw it into a room and trust that every corner of that room is lethal, regardless of furniture, interior walls, or improvised cover.
"A grenade utilizing BOP can clear a room of enemy combatants quickly leaving nowhere to hide while ensuring the safety of friendly forces," Morris said in the Army statement.
The M67 Isn't Going Away
The Army was careful to frame the M111 as a complement to the M67, not a replacement. The M67 remains in service, and according to the Army's release, troops will continue to use it in open terrain "to maximize lethal fragment effects." The M111 is for enclosed and restricted environments where fragmentation is dangerous to friendly forces.
Tiffany Cheng, a DEVCOM Armaments Center engineer who helped develop the M111 at Picatinny Arsenal, described the tactical logic in the Army statement: "We've given our Soldiers and joint warfighters the flexibility to determine in the field which type of grenade will best suit the current situation they are facing, be it open space or confined area."
The Army also engineered the transition to minimize training disruption. Both grenades use the same five-step arming process, and the M111 shares fuze components with the M67 and its training counterpart, the M69. A soldier switching between the two in the field encounters no procedural difference in how to arm or throw them.
"By standardizing the arming process and the fuzing, the Army saves taxpayer money without sacrificing lethality on the battlefield," Morris said in the Army statement. "This is the kind of acquisition reform that is currently underway throughout the Army acquisition enterprise."
A Lineage That Traces to the Trenches
The M67's longevity is exceptional even by military standards. It entered service in 1968 as American forces were deep in combat in Southeast Asia, succeeding the M26 grenades soldiers carried in Korea and the iconic Mk 2 — the "pineapple grenade," named for its appearance — that was introduced in World War I and served through World War II and beyond. In more than 55 years of continuous service, the M67 has been used in every major American conflict from Vietnam through Afghanistan and Iraq.
According to Military.com, the M67 carries 6.5 ounces of Composition B explosive — a mixture of RDX and TNT — with a lethal radius of 5 meters, a casualty-producing radius of 15 meters, and fragments capable of reaching 230 meters. It is, by any measure, a proven weapon. The problem was never its lethality in the open. The problem was what happened when soldiers tried to use it where modern warfare increasingly takes place: inside.
The concept of maintaining separate offensive and defensive grenades for different combat situations is not a new one. Military.com notes that the Soviet military built the offensive-defensive split into its doctrine decades before the United States did. The Soviet RGD-5 offensive grenade, which entered service in 1954, was designed with a tighter fragmentation radius to allow soldiers to throw it while moving without self-endangerment. The F-1 defensive grenade was designed for troops behind cover holding position against assault. Both remain in service with Russian and Ukrainian forces in current combat operations.
The Marines Are Also Upgrading
The Army's M111 isn't the only BOP grenade entering U.S. service. According to CNN's reporting, citing U.S. government contracting data, the U.S. Marine Corps is also acquiring the M21, a blast overpressure grenade manufactured by Norwegian company Nammo. The parallel acquisitions suggest broad institutional consensus within the U.S. military that fragmentation alone is insufficient for the urban combat environments American forces are likely to face.
The M21 and M111 reflect a generation of lessons learned at immense cost — in lives, in friendly-fire incidents, in the grinding, room-by-room attrition of Fallujah and Mosul and Kandahar — now finally encoded into the weapons soldiers and Marines carry.
The Bottom Line
The M111 Offensive Hand Grenade is a small weapon with a long backstory. It took 58 years of continuous service with an imperfect tool, two major urban wars, and the near-complete withdrawal of its predecessor for a health hazard before the Army finally fielded something purpose-built for the way modern ground combat actually works. The physics of blast overpressure have been understood for decades. The operational need was obvious after the first street-fighting in Iraq. The question was always whether the acquisition system would catch up before soldiers paid any more of the price for the gap.
The M111 is now cleared for full service. That it took until 2026 to get here says something about the pace of military acquisition. That it exists at all says something about what happens when enough soldiers come home and describe what they needed that they didn't have.