Operation Polka Dot was a U.S. Army test of a biological cluster bomb

Cluster bomb

A cluster munition is a form of air-dropped or ground-launched explosive weapon that releases or ejects smaller sub-munitions. Commonly, this is a cluster bomb that ejects explosive bomblets that are designed to kill enemy personnel and destroy vehicles...

 during the early 1950s.

Operation

Operation Polka Dot was a field test of the E133 cluster bomb

E133 cluster bomb

-History:The U.S. E133 cluster bomb was developed prior to Richard M. Nixon's 1969 declaration that ended the U.S. biological weapons program. At the time of Nixon's declaration the E133 was considered the most likely candidate in the U.S. biological arsenal to actually be used in a combat...

 undertaken at Dugway Proving Ground

Dugway Proving Ground

Dugway Proving Ground is a US Army facility located approximately 85 miles southwest of Salt Lake City, Utah in southern Tooele County and just north of Juab County...

 in Utah during the early 1950s. The operation was detailed in a July 18, 1955 U.S. Army report that also detailed Operation Trouble Maker. The operation was classified "secret" and involved filling the munitions with the biological agent

Biological agent

A biological agent — also called bio-agent or biological threat agent — is a bacterium, virus, prion, or fungus which may cause infection, allergy, toxicity or otherwise create a hazard to human health. They can be used as a biological weapon in bioterrorism or biological warfare...

 simulant, Bacillus globigii.