First and Second World Wars
The first strategic bombing efforts took place during World War I (1914–18), by the Russians with their Sikorsky Ilya Muromets bomber (the first heavy four-engine aircraft), and by the Germans using Zeppelins or long-range multi-engine Gotha aircraft. Zeppelins reached England on bombing raids by 1915, forcing the British to create extensive defense systems including some of the first anti-aircraft guns which were often used with searchlights to highlight the enemy machines overhead. Late in the war, American fliers under the command of Brig. Gen. Billy Mitchell were developing multi-aircraft "mass" bombing missions behind German lines, although the Armistice ended full realization of what was being planned.
Study of strategic bombing continued in the interwar years. Many books and articles predicted a fearful prospect for any future war, paced by political fears such as those expressed by British Prime Minister Stanley Baldwin who told the House of Commons early in the 1930s that "the bomber will always get through" no matter what defensive systems were undertaken. It was widely believed by the late 1930s that strategic "terror" bombing of cities in any war would quickly result in devastating losses and might decide a conflict in a matter of days or weeks. But theory far exceeded what most air forces could actually put into the air. Germany focused on short-range tactical bombers. Britain's Royal Air Force began developing four-engine long-range bombers only in the late 1930s. The U.S. Army Air Corps (Army Air Forces as of mid-1941) was severely limited by small budgets in the late 1930s, and only barely saved the B-17 bomber that would soon be vital. The equally important B-24 first flew in 1939. Both aircraft would constitute the bulk of the American bomber force that made the Allied daylight bombing of Nazi Germany possible in 1943–45.
At the start of World War II, so-called "strategic" bombing was initially carried out by medium bomber aircraft which were typically twin-engined, armed with several defensive guns, but only possessed limited bomb-carrying capacity and range. Both Britain and the US were developing larger two- and four-engined designs, which began to replace or supplement the smaller aircraft by 1941–42. After American entry into the war, late, in 1941, the U.S. 8th Air Force began to develop a daylight bombing capacity using improved B-17 and B-24 four-engine aircraft. In order to assemble the formations to carry out these bombing campaigns, assembly ships were used to quickly form defensive combat boxes. The RAF concentrated its efforts on night bombing. But neither force was able to develop adequate bombsights or tactics to allow for often-bragged "pinpoint" accuracy. The post-war U.S. Strategic Bombing Survey studies supported the overall notion of strategic bombing, but underlined many of its shortcomings as well. Attempts to create pioneering examples of "smart bombs" resulted in the Azon ordnance, deployed in the European Theater and CBI Theater from B-24s.
Following the untimely death of the top German advocate for strategic bombing, General Walther Wever in early June 1936, the focus of Nazi Germany's Luftwaffe bomber forces, the so-named Kampfgeschwader (bomber wings) became the battlefield support of the German Army as part of the general Blitzkrieg form of warfare, carried out with both medium bombers such as the Heinkel He 111, and Schnellbombers such as the Junkers Ju 88A. General Wever's support of the Ural bomber project before WW II's start dwindled after his passing, with the only aircraft design that could closely match the Allied bomber force's own aircraft – the early November 1937-origin Heinkel He 177A, deployed in its initial form in 1941–42, hampered by a RLM requirement for the He 177A to also perform medium-angle dive bombing, not rescinded until September 1942 – unable to perform either function properly, with a powerplant selection and particular powerplant installation design features on the 30-meter wingspan Greif, that led to endless problems with engine fires. The March 1942-origin, trans-Atlantic ranged Amerika Bomber program sought to ameliorate the lack of a seriously long-ranged bomber for the Luftwaffe, but resulted with only three Messerschmitt-built and a pair of Junkers-built prototypes ever flown, and no operational "heavy bombers" for strategic use for the Third Reich, outside of the roughly one thousand examples of the He 177 that were built.
By the end of the Second World War in 1945, the "heavy" bomber, epitomized by the British Avro Lancaster and American Boeing B-29 Superfortress used in the Pacific Theater, showed what could be accomplished by area bombing of Japan's cities and the often small and dispersed factories within them. Under Major General Curtis LeMay, the U.S. 20th Air Force, based in the Mariana Islands, undertook low-level incendiary bombing missions, results of which were soon measured in the number of square miles destroyed. The air raids on Japan had withered the nation's ability to continue fighting, although the Japanese government delayed surrender, resulting the atomic bombs dropped on Hiroshima and Nagasaki in August 1945.
The Cold War and its aftermath
During the Cold War, the United States and United Kingdom on one side and the Soviet Union on the other kept strategic bombers ready to take off on short notice as part of the deterrent strategy of mutual assured destruction (MAD). Most strategic bombers of the two superpowers were designed to deliver nuclear weapons. For a time, some squadrons of Boeing B-52 Stratofortress bombers were kept in the air around the clock, orbiting some distance away from their fail-safe points near the Soviet border.
The British produced three different types of "V bombers" for the Royal Air Force which were designed and designated to be able to deliver British-made nuclear bombs to targets in European Russia. These bombers would have been able to reach and destroy cities like Kiev or Moscow before American strategic bombers. While they were never used against the Soviet Union or its allies, two types of V bombers, the Avro Vulcan and the Handley Page Victor were used in the Falklands War towards the end of their operational lives.
The Soviet Union produced hundreds of unlicensed, reverse-engineered copies of the American Boeing B-29 Superfortress, which the Soviet Air Forces called the Tupolev Tu-4. The Soviets later developed the jet-powered Tupolev Tu-16 "Badger".
The People's Republic of China produced a version of Tupolev Tu-16 on license from the Soviet Union in the 1960s which they named the Xian H-6.
During the 1960s France produced its Dassault Mirage IV nuclear-armed bomber for the French Air Force as a part of its independent nuclear strike force, the Force de Frappe, using French-made bombers and IRBMs to deliver French-made nuclear weapons. Mirage IVs served until mid-1996 in the bomber role, and to 2005 as a reconnaissance aircraft.
Today the French Republic has limited its strategic armaments to a squadron of four nuclear-powered ballistic missile submarines, with 16 SLBM tubes apiece. France also maintains an active force of supersonic fighter-bombers carrying stand-off nuclear missiles such as the ASMP, with Mach 3 speed and a range of 500 kilometers. These missiles can be delivered by the Dassault Mirage 2000N and Rafale fighter-bombers; the Rafale is also capable of refueling others in flight using a buddy refueling pod.
Newer strategic bombers such as the Rockwell International B-1B Lancer, the Tupolev Tu-160, and the Northrop Grumman B-2 Spirit designs incorporate various levels of stealth technology in an effort to avoid detection, especially by radar networks. Despite these advances earlier strategic bombers, for example the B-52 (last produced in 1962) or the Tupolev Tu-95 remain in service and can also deploy the latest air-launched cruise missiles and other "stand-off" or precision guided weapons such as the JASSM and the JDAM.
The Russian Air Force's new Tu-160 strategic bombers are expected to be delivered on a regular basis over the course of 10 to 20 years. In addition, the current Tu-95 and Tu-160 bombers will be periodically updated, as was done during the 1990s with the Tu-22M bombers.
Strategic bombers of the Cold War were primarily armed with nuclear weapons. During the post-1940s Indochina Wars, and also since the end of the Cold War, modern bombers originally intended for strategic use have been exclusively employed using non-nuclear, high explosive weapons. During the Vietnam War, , Operation Freedom Deal, Gulf War, military action in Afghanistan, and the 2003 invasion of Iraq, American B-52s and B-1s were mostly employed in tactical roles. During the Soviet-Afghan war in 1979–88, Soviet Air Forces Tu-22Ms carried out several mass air raids in various regions of Afghanistan.