Carpet bombing was introduced during World War II.

Actually it was first used in Spain during the Spanish Civil War. The bombing operations were carried out by the German Condor Legion against the Republican Infantry Legion. Later on the Germans used carpet bombing as part of their invasion in Europe. Later on the Allies would also employ carpet bombing on the Germans and later on the Japanese. Today the use of carpet bombing is now considered a war crime as it leaves many people dead or wounded as well as the destruction of buildings and homes.