Saturation bombing

Carpet bombing, also known as saturation bombing, is a large aerial bombing done in a progressive manner to inflict damage in every part of a selected area of land. The phrase evokes the image of explosions completely covering an area, in the same way that a carpet covers a floor. Carpet bombing is usually achieved by dropping many unguided bombs.

The term obliteration bombing is sometimes used to describe especially intensified bombing with the intention of destroying a city or a large part of the city. The term area bombing refers to indiscriminate bombing of an area, and also encompasses cases of carpet bombing, including obliteration bombing. It was used in that sense especially during World War II. Carpet bombing of cities, towns, villages, or other areas containing a concentration of civilians is considered a war crime as of the 1977 of the Geneva Conventions.

One of the first cases of carpet bombing was by the German Condor Legion during the Spanish Civil War against Republican infantry during the Battle of El Mazuco, fought between 6 and 22 September 1937, where the targeted troops were dispersed on rocky slopes and the Condor Legion learned that carpet bombing was not very effective in such terrain.

In the European Theatre, the first city to suffer heavily from aerial bombardment was Warsaw on 25, September 1939. Continuing this trend in warfare the Rotterdam Blitz was an aerial bombardment of Rotterdam by 90 bombers of the German Air Force on 14 May 1940, during the German invasion of the Netherlands. The objective was to support the German assault on the city, break Dutch resistance and force the Dutch to surrender. Despite a ceasefire, the bombing destroyed almost the entire historic city centre, killing nearly nine hundred civilians and leaving 30,000 people homeless. The destructive success of the bombing led the Oberkommando der Luftwaffe (OKL) to threaten to destroy the city of Utrecht if the Dutch Government did not surrender. The Dutch capitulated early the next morning.

...
Wikipedia