Explained | How BLU-109 'bunker buster' bombs could potentially decimate Hamas tunnels in Gaza

Israel has got large 'bunker buster' bombs from the United States among tens of thousands of other weapons and weaponry as part of longtime military cooperation between the two countries. The delivery of these weapons has been aimed to help Israel in its ongoing wartime effort to dislodge Palestinian group Hamas — declared a terrorist group by Israel, the US, and the UK among others — from Gaza, according to the US officials. 

The supply of arms includes roughly about 15,000 bombs and 57,000 artillery shells which the United States supplied shortly after the Oct 7 attack by Hamas on southern Israel that killed about 1200 Israelis. The retaliatory state of war which resumed on December 1 after a brief truce, has killed more than 15,000 Palestinians in Gaza, according to Hamas-controlled Gaza health ministry.

Among the munitions the U.S. has transferred to Israel are more than 5,000 Mk82 unguided or "dumb" bombs, more than 5,400 Mk84 2,000 pound warhead bombs, around 1,000 GBU-39 small diameter bombs, and approximately 3,000 JDAMs, which turn unguided bombs into guided "smart" bombs, Wall Street Journal reported.

The US has also sent Israel roughly 57,000 155mm artillery shells – a key munition the U.S. has also provided Ukraine since the 2022 Russian invasion – along with thousands of other artillery shells and various small arms.

What does it mean?

Israel has attempted to establish the existence of an elaborate web of tunnels in Gaza. These tunnels, both Israel and the United States have said, are used to launch attacks on Israel from inside Gaza Strip. In Gaza, Hamas’ military wing uses this vast network of underground tunnels, which Israel could attempt to strike with the bunker busters.

The tunnels, however, lie beneath Gaza’s urban landscape of apartment blocks, schools, hospitals, and other civilian buildings.

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But the unprecedented scale of civilian casualties in Gaza has alarmed Western capitals. The United States is also urging Israel to consider preventing large-scale civilian casualties while supplying many of the munitions deployed. 

"I made clear that after a pause, it was imperative that Israel put in place clear protections for civilians, and for sustaining humanitarian assistance going forward," Secretary of State Antony Blinken said in Dubai on Friday. 

Supply of BLU-109 bunker buster bombs and their potential impact on Hamas' tunnels in Gaza

The BLU-109 bunker buster carries a 2,000 pound warhead and is designed to penetrate a concrete shelter. These bombs were used by the US during the Gulf War in 1991 as well as during the invasion of Afghanistan after 9/11 attacks.

The BLU-109 can penetrate about 1.8 metre or 6 feet of reinforced concrete. That is, they are designed to penetrate through a target underground instead of conventional carpet bombing on surface. The extra speed provided by a rocket enables greater penetration of a missile-mounted bunker buster warhead. To ensure maximum penetration (impact depth), the warhead with BLU-109 usually consists of a high-density projectile only.

"There is potentially a legitimate use for these things, to bust underground bunkers," Brian Finucane, a senior adviser at the nonprofit International Crisis Group, and a former attorney-adviser at the State Department was quoted as saying by the Wall Street Journal. 

"The problem is there’s a massive refugee camp with hundreds of thousands of civilians on top of those tunnels when you drop the bomb. You need to factor in the harm to civilians."

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Notably, the US said that Israel used an American-provided bomb during its strike at crowded Jabalia refugee camp in Gaza in October, an attack that levelled an apartment block there and killed more than 100 people. Israel claimed the strike killed a Hamas leader.

Experts point out that the transfer of such weaponry to Israel shows the kind of choices Israel is facing while attempting its stated goal to decimate Hamas in Gaza, one of the world's most densely populated regions. 

Israel-Hamas war: The network of tunnels in Gaza Strip

Qatar-based Hamas leader, Yahya Sinwar, had claimed in 2021 that there were 310 miles of tunnels in Gaza. 

The US officials cited in the western media say that the tunnels in Gaza exist as "miniature cities" with rooms, cells and even roads for vehicles. 

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Besides, since taking over Gaza in 2007, Hamas has invested huge but unspecified amounts of money to revamp the existing tunnel infrastructure and create new ones. The tunnels are used to smuggle weapons, militants, politicians, food and goods necessary to make the rockets often fired into Israel from inside the strip.

(With inputs from agencies)