Strategic bombing
Strategic bombing is the use of bomber aircraft, operating independently or with support aircraft, to attack the homeland military forces, industry and population of a nation. The idea was first formally proposed by the Italian theorist, Giulio Douhet, in 1917. It was a major part of the Second World War, and, with the advent of nuclear weapons, was a key part of the Cold War.
In the Cold War and present context, strategic bombing is a subset of strategic strike, which can involve both "kinetic" attacks by bombers, intercontinental ballistic missiles, cruise missiles, and submarine-launched ballistic missiles, as well as nonkinetic attacks using information operations including electronic warfare.
Second World War
Germany
Germany was burned out and lost the war in large part because of strategic bombing. Targeting became somewhat more accurate in 1944, but the real solution to inaccurate bombs was more of them. The AAF dropped 8 million bombs (1.6 million tons) against Germany using the B-17 and B-24. Besides knocking out the Luftwaffe, the second most striking achievement of the strategic bombing campaign was the destruction of the German oil supply. Oil was essential for U-boats and tanks, while very high quality aviation gasoline was essential for piston planes. Germany had few wells, and depended on imports from Russia (before 1941) and Nazi ally Romania, and on synthetic oil plants that used chemical processes to turn coal into oil. Heedless of the risk of Allied bombing, the Germans had carelessly concentrated 80% of synthetic oil production in just 20 plants. These became a top priority for the AAF and RAF in 1944, and were targets for 210,000 tons of bombs. The oil plants were very hard to hit, but also hard to repair. The strategic bombings by the AAF and RAF dried up the oil supply in the summer of 1944. An extreme oil emergency followed, which grew worse month by month.
The third notable achievement of the bombing campaign was the degradation of the German transportation system--its railroads and canals (there was little truck traffic.) In the two months before and after D-Day the American Liberators (B-24), B-17 Flying Fortresses and British Lancasters hammered away at the French railroad system, complemented by Resistance fighters sabotaged some 350 locomotives and 15,000 freight cars every month. Critical bridges and tunnels were cut. Berlin responded by sending in 60,000 German railway workers, but even they took two or three days to reopen a line after heavy raids on switching yards. The system deteriorated quickly, and it proved incapable of carrying reinforcements and supplies to oppose the Normandy invasion. To that extent the assignment of strategic bombers to the tactical job of interdiction was successful.
When Bomber Command hit German cities, it inevitably hit some railroad yards. The AAF made railroad yards a high priority, and gave considerable attention as well to bridges, moving trains, ferries, and other choke points. The "transportation policy" of targeting the railroad system came in for intense debate among Allied strategists. It was argued that enemy had the densest and best operated railway system in the world, and one with a great deal of slack. The Nazis systematically looted rolling stock from conquered nations, so they always had plenty of locomotives and freight cars. Furthermore, most traffic was "civilian," and urgent troop train traffic would always get through. The critics exaggerated the resilience of the German system. As wave after wave of bombers blasted away, repairs took longer and longer. Delays became longer and more frustrating.
Troop trains usually got through, but the "civilian" traffic that did not get through comprised food, uniforms, medical equipment, horses, fodder, tanks, fuel, howitzers, flak shells and machine guns for the front lines, and coal, steel, spare parts, subassemblies, and critical components for munitions factories. By January, 1945, the transportation system was cracking in dozens of places, and front-line units had more luck trying to capture Allied weapons than waiting for fresh supplies of their own.
Vietnam War
During the Vietnam War, there were a variety of strike operations against North Vietnam. Operation Rolling Thunder was essentially futile. With less restrictive rules of engagement, Operation Linebacker I was effective at the operational level. Operation Linebacker II was decisive in achieving a specific short-term strategic goal.
Falklands War
Perhaps the most complex operation using conventional bombs, the British "BLACK BUCK" raids during the Falklands War were effective, again for a specific objective.
Iraq War
The most effective large-scale strike campaign, considering both the results and the strategic goals, was Operation Desert Storm. Subsequent strike operations in the Balkans and Iraq War were more limited, in part due to a lack of suitable targets.