Explained: What is a cluster bomb? The weapon Iran used in missile strike on Israel

The ongoing hostilities between Israel and Iran took a concerning turn on Thursday when the Israeli military claimed that Iran had fired a missile armed with a cluster munition warhead at a populated area in central Israel, marking the first such reported use in the current conflict.

The missile struck Or Yehuda and nearby towns, scattering bomblets across residential zones, as per The New York Times. While there were no reported casualties, the deployment of such a weapon, widely considered dangerous and indiscriminate, triggered immediate international concern.According to Israeli officials, the warhead released multiple submunitions over a wide radius, including areas near a hospital and on residential properties. The Home Front Command warned civilians that unexploded bomblets remain a threat and could still detonate. According to The Times, videos show several impact craters, and unexploded ordnance resembling known submunitions from Iranian ballistic missiles was also found.

What are cluster bombs?

Cluster bombs, also called cluster munitions, are explosive weapons that disperse smaller bombs, known as submunitions or bomblets, over a wide area before impact.

These bomblets are designed to explode upon hitting the ground or after a delay. However, many fail to detonate, remaining live and lethal for months or even years, posing long-term risks to civilians.As per the United Nations Office for Disarmament Affairs, cluster bombs are either air-dropped or ground-launched and can saturate areas as large as several football fields, making them particularly lethal in densely populated areas.

“They are egregious weapons with their wide-area destruction… especially if used in a civilian populated area,” said Daryl Kimball, executive director of the Arms Control Association, as quoted by Reuters.The submunitions, often grenade-sized with fins or streamers for stabilisation, are designed to cause damage to both personnel and unarmoured vehicles. Some modern versions, like the US-made DPICM, feature dual-purpose charges for added effect.

But the biggest controversy lies in their high “dud rate”, failure to explode on impact, which turns them into de facto landmines. Dud rates can range from 2% to 40%, depending on the manufacturer, according to the American think tank Centre for Strategic and International Studies (CSIS).

Why are they banned?

The 2008 Convention on Cluster Munitions (CCM), which entered into force in 2010, bans the use, development, production, acquisition, and transfer of cluster munitions.

So far, 111 countries and 12 other entities have signed the treaty.But key nations, including Israel, Iran, the United States, Russia, China, and India, have not joined. As per the United Nations, 99% of declared global stockpiles have been destroyed under the treaty.Human Rights Watch's Bonnie Docherty explained that cluster munitions "cannot distinguish between soldiers and civilians because they spread their submunitions over a wide area and leave behind unexploded submunitions that endanger civilians… like land mines.”Israel has previously used cluster bombs, most notably during the 2006 Lebanon war. More recently, both Russia and Ukraine have employed them in their ongoing war, and the US controversially supplied Ukraine with cluster munitions in 2023, as per CSIS.Iran’s alleged use of a cluster-armed missile, likely a Qiam or Khorramshahr, which can carry dozens of submunitions, suggests a shift in military strategy to maximise target area coverage, even at the risk of civilian harm.

“Sometimes you might not need that much destructive force,” said Fabian Hinz of the International Institute for Strategic Studies. “Just having a geographical spread… could be worth it,” he was quoted as saying by The New York Times.Israeli Prime Minister Netanyahu, without using the term "cluster," confirmed that a “fragmenting warhead” had been used, describing the submunitions as “smaller bombs that if you touch them they explode.”As both Iran and Israel escalate military operations, the use of such controversial weapons signals not only increased intensity but raises humanitarian alarms over the long-term dangers to civilians, dangers that may persist well after the last missile falls.