What are the 'bunker buster bombs' that Israel could use?

In an effort to dissuade Hezbollah from retaliating after Israel assassinated its top military commander Fouad Shukur in the southern suburbs of Beirut, the party has received warnings from multiple sources that Israel is prepared to respond swiftly and forcefully to any attack, potentially using bunker-buster bombs on underground military targets in southern Lebanon.

What are bunker-buster bombs?

Bunker busters, manufactured primarily in the United States, are specialized munitions designed to penetrate deep into fortified structures or underground installations before exploding. Featuring reinforced noses and heavy shells, they burrow through layers of earth, concrete, or steel, gaining power to penetrate tough materials. Once they reach a certain depth, they detonate, maximizing damage to underground targets while minimizing impact on the surface. This makes them particularly effective weapons for destroying bunkers, tunnels, or military installations buried deep underground.

These munitions were first used against German underground munitions factories during World War II. However, their modern versions originated during the Vietnam War when the United States sought to destroy the enemy's vast underground tunnel networks. Since then, these ground-penetrating bombs have been used in the Middle East, notably against Iraq in 1991 and 2003 when the United States targeted fortified Iraqi command centers, and by Israel in Gaza against Hamas tunnels, notably in 2014 and 2021.

What targets could be targeted?

Israel’s interest in bunker-buster bombs is not new, as Iran buries its strategic nuclear facilities nearly 100 meters underground, and Hezbollah, like Hamas in Gaza, has a vast network of tunnels in southern Lebanon. Some estimate that they extend as far as seven kilometers into the country. These tunnels are essential to the party’s operations, allowing it to store weapons and move fighters while avoiding detection by Israeli surveillance systems. Hezbollah, Hamas and Iran are said to use reinforced concrete and build facilities at significant depths to avoid detection and damage from bunker-buster bombs. As an expected Iranian response to the assassination of Ismail Haniyeh in Tehran on July 31 keeps the region on alert, a Lebanese source close to Hezbollah told the Washington Post that Iran would be concerned about possible American and Israeli strikes on its nuclear program in the event of a generalized conflict.

By striking these underground targets from the air, Israel would seek to avoid the dangers and difficulties associated with sending troops on the ground. Since 2000, these bombs have been part of the Israeli military arsenal, with the first international delivery of GBU-28 bunker-buster bombs in 2005. Initially developed during the Gulf War in 1991, this American weapon is the ancestor of new generations of bunker-buster bombs. Today, with a weight of 30,000 pounds (or 13.6 tons), Washington produces the largest non-nuclear bomb in the world, capable of piercing 60 meters of concrete before exploding. This mega-bomb, whose production the United States accelerated in May to produce six to eight per month, compared to two previously, according to Bloomberg, can only be dropped from a B-2 Stealth bomber. Since 2021, Israel has been hoping to acquire the GBU-72 bomb (weighing about 5,000 pounds, or 2.2 tons) from its ally, as both countries seek to prevent Iran from being able to produce a nuclear weapon.

What does international law say?

The use of bunker-buster bombs is not strictly illegal but must comply with fundamental principles of international law, such as precaution and proportionality. They should therefore not be used where there is a high probability of civilian casualties or where similar results can be achieved with less destructive weapons.

While the U.S. has delivered 100 BLU-109 bunker-buster bombs to Israel since Oct. 7, according to media reports in December, Washington suspended a 2,000-pound (over 900 kg) arms shipment in May, which may have included such munitions. The move reflects U.S. and international concerns over the civilian casualties in Gaza, which now stand at nearly 40,000 dead and over 92,000 injured, as the International Court of Justice has repeatedly ordered provisional measures to prevent genocide in the Palestinian enclave. Unverified reports suggest that some munitions used in the war that has raged for over 10 months may be bunker-buster bombs.

This article originally appeared in French in L'Orient-Le Jour.