Saturation bombing, aka 'carpet bombing', is for when there is a need for indiscriminate destruction inside a defined area.
That is -- indiscriminate
INSIDE an area.
Saturation bombing a la B-52 is not as mindless as some people would like to believe and often they will bring up WW II or the Vietnam War to illustrate. In some ways, they are correct, but in other ways, incorrect.
Indiscriminate bombing is wasteful, even during WW II when the resources of the nation were mobilized to the war effort. But in WW II, technology were not available to reduce the CEP of each 'dumb' gravity bomb, so bombardiers and pilots did the best they could to do what have always been the goal -- indiscriminate destruction inside a defined area.
When, in the course of an air campaign, is there such a need and when will that area be available ?
- If you need precision bombing capable fighter-bombers elsewhere. In this case, if the target is high enough of a priority, saturation bombing will be needed, assuming you have that capability like the US does.
- If the target is far away enough from non-combatants. In this case, saturation bombing saves time and resources.
We are moving away from WW II where saturation bombing was used to break the will of a people along with means to wage a war.
http://www.pbs.org/wgbh/americanexperience/features/primary-resources/truman-leaflets/
This was just one of many types of leaflets dropped on Japanese cities warning of impending destruction.
We do not want to return to those days.
Saturation bombing do have its place in the methods of air warfare, whether it is for tactical or strategic goals.
Saturation bombing at the tactical level immediately deny the enemy of vital front line resources, most vital of all is land. The destruction of land surfaces deny the use of tanks, artillery and rocket emplacements, troop movements, and even entrapment of large concentration of ground forces. Imagine a river at your back while the ground in front of you is afire.
Saturation bombing at the strategic level deny the enemy his own means to wage war and has political motivation and consequences.
Warfare has two main types: Tactical and Strategic.
Tactical warfare is for when the two sides wishes to fight to a stalemate. Armies either do not violate borders or trespass only into short distances. Air forces conducts quick deep strikes but the bulk of their sorties are for front line battles. Basically, the two sides want to demonstrate their resolves to each other into mutual withdrawal to their respective borders.
Strategic warfare is for when both sides absolutely seeks to subjugate each other. It is not enough that the army is destroyed on the front lines, its support at home must be broken as well. Occupation often follows such defeat. The defeated government is either removed and replaced or removed completely and the country is somehow possessed.
Strategic saturation bombing accelerate the strategic defeat of the enemy. It may sound strange, but saturation bombing today can be precise, or more precise than its WW II predecessor. There is no need to destroy a city, but deny that city electricity, food, and water maybe enough to induce into the government the desire for surrender.
Fighter-bombers are the air weapons of choice for countries that must import their defense. Because of this, wars between countries will lean more towards the tactical type. An example is the Iraq-Iran War. Both sides gained no real advantages over the other simply because neither side can make any strategic damages to the other. The result was the war were confined to the borders.