Anti-tank dogs were dogs that were trained by Soviet and Russian military forces, between 1935 and 1996, to carry explosives to tanks, armored vehicles, and other military targets.
The training procedure was pretty simple: starve the dogs and teach them that all food was to be found under enemy tanks and armored vehicles. When the dogs slipped under a tank or an armored vehicle, a small wooden lever would be tripped and the explosives detonated where there was less armor.
One problem was that when the dogs were actually used during World War II, they had been trained on diesel powered Soviet tanks and so would would sometimes turn around and attack the Soviets’ own forces rather than seek out the German gasoline-powered vehicles.
Other times the dogs would spook at the rumble of engines, gunfire, and explosives on the battlefield, and would run away, becoming a kind of four legged "wild weasel" bomb that might end up anywhere killing almost anything.
Despite the problems, Russian anti-tank dogs were reported to have disabled 300 German tanks during WWII, though most historians think these numbers are propaganda, and that the true success rate was closer to a few dozen tanks despite thousands of dogs deployed.
Japan, Vietnam, and the U.S. have also tried using dogs to carry explosives into fortified positions such as machine gun nests, but the results have always been poor due to dog disobedience or intelligence.
During the Iraq war, more success was achieved using donkeys, which can carry larger amounts of explosive and which proved to be more reliable under battlefield conditions.