US strikes on Iran nuclear sites: What are B-2 bombers, bunker busters?

The Massive Ordnance Penetrator (MOP), officially designated as GBU-57A/B, is the largest non-nuclear bomb in the US military arsenal, specifically engineered to destroy deeply buried and hardened underground targets such as bunkers, nuclear facilities, and reinforced command centers. In short, a 'bunker buster'.

Built by Boeing and guided by GPS, it is engineered specifically to target deeply buried and hardened bunkers. Boeing has been working under a Pentagon contract with at least 20 units built by 2025.

A US Air Force fact sheet cited by CBS News says the MOP measures 20.5 feet in length and 31.5 inches in diameter, and weighs just under 30,000 pounds — including 5,300 pounds of high-explosive material.

The bomb can burrow more than 200 feet through reinforced concrete before detonating. Its casing, made from high-performance steel alloy, helps it withstand the immense impact forces upon penetration. The MOP’s explosive yield is more than 10 times greater than that of its predecessor, the BLU-109.

Source: @Mohinde15051982/X) Israeli strikes on Iran killed 865 people, wounded 3,396 others: Human rights group

Only the B-2 Spirit stealth bomber is capable of carrying and deploying the MOP. The B-2’s stealth capability allows it to evade radar and air defenses, making it the ideal platform for strikes on heavily protected sites like Fordow. Each B-2 can carry up to two MOPs in its internal weapons bay.

An unconfirmed report by the New York Times claimed that the B-2 bombers which struck Iran’s nuclear sites flew non-stop for 37 hours straight from their base in Missouri, refuelling multiple times mid-air during the long-range mission.

The US targeted Fordow, Natanz, and Isfahan nuclear sites in Iran on June 21, joining Israel in its aggression against the sovereign Iranian state.

Six 30,000-pound “bunker-buster” warheads were used to strike Fordow nuclear site, which is located 90 meters underground below a… pic.twitter.com/6aOBry88S8

— TRT World (@trtworld) June 22, 2025

According to experts, the MOP can’t guarantee complete destruction of the Iranian enrichment plant of Fordow’s central vault in one hit owing to the plant's extreme depth. However, using multiple MOPs to strike entrances, support systems, and structural components could still disrupt or disable the site effectively — even if some underground chambers remain intact. The true extent of damage is still unverified, with credible reports pointing to limited impact in key hardened areas.

Meanwhile, in response to US strikes — particularly the ones that reportedly targeted Iran’s Fordow nuclear facility on Saturday, 21 June (US Eastern time, early Sunday morning IST) — Iran is widely expected to consider retaliatory options, and US military assets across the Middle East are potential targets.

The USA 🇺🇸 is the only country having the bunker buster bombs that can penetrate deeply under the ground. And, B2 stealth bomber can carry the bombs.
(Source: Public) pic.twitter.com/tWWDAvkMam

— Bac Tran (@globalvoice306) June 21, 2025

LIVE Iran-Israel War: Defiant Iran launches more missiles at Israel, air raid sirens fail to sound in Haifa

A look at some of the major ones:

Al Udeid Air Base: The base is located in Qatar and is the largest US military base in the Middle East.

US Navy Fifth Fleet: The headquarters are in Bahrain and are a critical asset in the Persian Gulf.

Al Asad Air Base: A US base in Iraq that Iran targeted in 2020 after the killing of Quds Force leader Qasem Soleimani. The installation houses thousands of American troops and is the site of the largest US deployment in the country.

Harir Air Base: The base in Erbil, Iraq, has been on the receiving end of Iranian-proxy group drone attacks.

Al Tanf Garrison: A US military base in southern Syria, near the borders of Iraq and Jordan.

Ali al-Salem Air Base: An air base in Kuwait and about 20 miles from the Iraqi border that houses members of the Air Force’s 386th Air Expeditionary Wing.

Al Dhafra Air Base: Located in the United Arab Emirates, the installation is home to the Air Force’s 380th Air Expeditionary Wing, which operates F-22 Raptor fighter jets and several kinds of surveillance planes and drones.

With inputs from New York Post, agencies