The theory was that the bats would be released just before dawn with incendiary devices with timers attached to each bat. As daylight approached, the bats would head for dark recesses of wooden Japanese houses. When the bats were safely asleep, the incendiary devices would ignite, thus producing a conflagration of unprecedented proportions.
A test run of this theory was carried out in the southwestern United States. However, the advent of the atomic bomb rendered this experiment moot.