Balloons have been used in many wars throughout history.
In the American Civil War a certain Professor Lowe became Balloonist #1 in the Army of the Potomac and used his hot air balloon to spy on confederate lines. In the Franco Prussian War (1870-1871), the citizens of Paris kept in touch during the German siege of their city via balloons. In World War One most of the combatants used both tethered and free balloons of every imaginable type for use in reconnaissance and even for attacks. Modern combat forces still use balloons, such as the Fulton Skyhook for various special uses.
There was however, only one nation that used balloons as unmanned bombers to attack their enemy's homeland thousands of miles away. That nation was the Empire of Japan who launched some 9300 of these devices during World War Two.
