This sounds like a plot element from the movie Inglorious Basterds, but it's true- British Special Forces used dead rats, among other things rigged with explosives, against Nazi forces during World War II.
Here's how those rat bombs were used:
But the most exotic device was the "explosive rat". A hundred of the rodents were procured by an SOE officer posing as a student needing them for laboratory experiments. The rats were skinned, filled with plastic explosive, and sewn up. The idea was to place a rat among coal beside a boiler. When they were spotted, they would immediately be thrown on to the fire, causing a huge explosion.
That was the theory. As one of the SOE files records: "This device caused considerable trouble to the enemy, but not quite in the way that was intended." The Germans intercepted the container of dead rats before they could be used for "operational purposes". But all was not lost. According to an SOE report, their discovery had an "extraordinary moral effect": the rodents were exhibited at all German military schools, prompting a hunt for "hundreds of rats the enemy believed were distributed on the continent".
SOE concluded: "The trouble caused to them was a much greater success to us than if the rats had actually been used."
Link --via i09