Operation (*) Fu-Go attached weapons to these things in an attempt to set forest fires and avenge the Doolittle Raid.  
In reaction to the use of these non-lethal things, the California Division of Forestry started the Firefly Project. These non-lethal things were the key component of a technology which killed the children of pastor Archie Mitchell on a family visit to Gearhart Mountain, Oregon.  The feasibility of using these things for a military operation traces back to a paper published in Esperanto by Wasaburo Ooishi.  Some of these things were hand-laminated by schoolgirls with a paste made from the konnyaku plant as part of an operation codenamed "paper".  Operation (*) Fu-Go attached weapons to these things in an attempt to set forest fires and avenge the Doolittle Raid.  For 10 points, Japan ineffectively attacked the continental United States during World War II with bombs attached to what types of inflatable devices?
In reaction to the use of these non-lethal things, the California Division of Forestry started the Firefly Project.
alloons [or fire balloons; or hydrogen balloons; or balloon bombs; or hot-air balloons; do not accept "weather balloons"] 