The United States on Saturday conducted a precision strike on Iranian nuclear facilities, including Fordow, Natanz, and Isfahan. This decisive blow to the Iranians involved over 125 military aircraft, including 7 B-2 stealth bombers, several fighter jets, refueling tankers, and surveillance/support aircraft. The operation also involved a single Ohio-class U.S. submarine that fired several guided missiles during the operation. About 75 precision-guided munitions were used during Operation Midnight Hammer. The most devastating munition, the GBU-57A/B Massive Ordnance Penetrator (MOP), was carried by the B-2 stealth bombers.
The B-2s were tasked with the most critical objective: reaching and destroying Iran’s nuclear infrastructure, one of which was buried deep in the mountains. For that mission, only one weapon was fit for the job. The MOP wasn’t just a part of the strike; it was the strike’s centerpiece, engineered specifically for a task like this.
The MOP before the operation had never been used in warfare. It is the largest bunker-busting bomb in the U.S. arsenal, with only 20 having been created, and a total of 14 used during the strike on Iran. So, how exactly does an MOP work?
Unlike conventional bombs that detonate on or just above the surface, bunker-busters are engineered to punch into the ground or through layers of reinforced concrete before detonating. The GBU-57 takes that to an extreme. Weighing over 30,000 pounds, it relies not just on explosive power, but on sheer kinetic force. Dropped from high altitude by a B-2 stealth bomber, the bomb uses its weight and reinforced casing to smash through dirt, steel, and concrete. It reportedly can penetrate up to 200 feet of earth or 60 feet of reinforced concrete. Only then does its delayed fuse trigger a high-powered detonation of approximately 5,300 pounds of explosives, maximizing destruction below the surface and collapsing whatever structures it hits from the inside out.
According to the Scientific American:
When dropped from 50,000 feet, the cruising ceiling for the B-2 Spirit bomber, the GBU-57/B uses sophisticated fins to guide it to its target. While the exact impact velocity is classified, it is estimated to exceed Mach 1—the speed of sound (767 mph). This strike delivers 800 to 900 megajoules (about 758,000 to 853,000 British thermal units) of kinetic energy—comparable to a 285-ton Boeing 747-400 touching down at 170 mph or a 565-ton Amtrak Acela train moving at 120 mph. With the bomb, however, all that energy is concentrated into a tiny area.
The penetration capabilities come directly from the kinetic energy generated by the MOP's weight and the height at which it is dropped. Only 20 percent of the total weight of the bomb is from the explosive; the rest is a hardened steel alloy that punches through whatever it needs to. The explosives are detonated by smart fuses that ignite once the munition has reached a desired depth. Some more advanced munitions are capable of detecting how many floors or voids the bomb has punched through and will detonate at a desired level.
Operation Midnight Hammer so far appears to be a massive success. Officials say that it can be reasonably assumed that the centrifuges at Fordow and Natanz were destroyed, but these reports cannot be confirmed. Vice President JD Vance himself has claimed in recent days that the setbacks the Iranians face in their nuclear enrichment program are "substantial."
.@VP: "I can say to the American people with great confidence that [Iran is] much further away from a nuclear program today than they were 24 hours ago. That was the objective of the mission." pic.twitter.com/Sr15c4xe3m
— Rapid Response 47 (@RapidResponse47) June 22, 2025