On the chopping block: cluster munitions and the law of war - unexploded submunitions from cluster bombs

Air Force Law Review, Spring, 2001 by Thomas J. Herthel

B. Cluster Munitions

Cluster munitions, in contrast to landmines (which are designed to lay dormant until disturbed), are "a group of smaller bombs which are dropped together" from aircraft, (29) and they are designed to explode at or near impact. Cluster munitions, also known as Cluster Bomb Units or "CBUs" (30) in the U.S. military, resemble, in size and weight, other unguided bombs. (31) Cluster bombs are made up of three main components: (1) a dispenser, often called a tactical munitions dispenser (TMD); (2) fuzes to control the weapon; and (3) submunitions, sometimes called bomblets (32) or "bombies." (33) "Once released, CBUs fall for a specified amount of time or distance before their dispensers open, allowing the submunitions to effectively cover a wide area target." (34)

An internal fuse tells each submunition when to detonate--either "above ground, at impact, or in a delayed mode." (35) Submunitions generally have an anti-tank, anti-material, or anti-personnel function. (36) While older variants contained only one type of submunition, new generation cluster bombs, called Combined Effects Munitions, engage an enemy in a variety of ways. (37) For example, the US Air Force's BLU 97/B Combined Effects Bomb combines "anti-armor, incendiary, and fragmentation effects, making it 'effective' against light armor and personnel." (38) To illustrate why cluster munitions are militarily significant, it is important to understand their history and development.

While landmine warfare against opposing armies began in the twelfth-century, the British designed cluster munitions during World War I for the purpose of incendiary attacks against the Germans. (39) By World War II, the United States and other nations were using cluster bombs that delivered fragmentation, chemical, and incendiary payloads. (40) Dubbed "wicked little weapons," by Brigadier General George C. Kenney, (41) the military extensively employed incendiary cluster munitions (mostly napalm) during bombing runs on Tokyo. (42) At the time, however, military planners did not consider cluster munitions very successful due to restrictive delivery devices and an inability to control submunition disbursement patterns. (43)

Following World War II and the conflict in Korea, the United States Navy undertook to develop more accurate cluster munitions by utilizing a newly conceived munitions dispenser. (44) The new dispenser, which began development in July 1959, ( was known as the "Eye-series." (46) Among the most successful in the series was the MK 20 Rockeye. The ordnance, complete with Mk 7 dispenser, Mk 339 time delay fuze, and 247 M118 anti-tank submunitions, (47) disbursed and scattered submunitions in an elongated, doughnut-shaped pattern whose size [was] controlled by the release height of the bomblets." (48) The Navy successfully completed the project by the mid-1960s. The Air Force also adopted it. (49)

By this time, the United States was deeply involved in the war in Vietnam (50) where use of cluster munitions proved particularly attractive. In Vietnam, US aircrews were especially susceptible to attack by anti-aircraft artillery (AAA), as well as the newly employed, Russian designed, surface-to-air missiles (SAM). (51) Because of the AAA and SAM threat, aircrews found it difficult to engage and neutralize the Vietnamese air defenses from altitudes that allowed using single bombs accurately and effectively. (52) Cluster munitions provided the solution; used as a flak-suppression weapon, they could deliver literally hundreds of bomblets with a singe pass, thereby eliminating the need for aircrews to fly at lower altitudes or over the same target more than a single time. (53)