Editing Bunker buster (section)

===World War II===

==== Germany ====
In World War II the [[Luftwaffe]] developed a series of [[German Rocket Propelled Bombs|unguided rocket-propelled armor-piercing bombs]] for use against shipping and fortifications.

====United Kingdom====
[[File:U-Boat Pen Grand Slammed.jpg|thumb|right|upright|A [[Submarine pen|U-Boat pen]] after being hit by a ''[[Grand Slam (bomb)|Grand Slam]]''. Note the figure standing on the pile of rubble.]]
[[File:Disney bomb impact test.png|thumb|alt=Diagram showing cross-sections of a hole punched through a thick roof|Diagram of a roof penetration produced by a [[Disney bomb]] striking the German, [[Valentin submarine pens|Valentin U-boat pen]]. The bomb was one of a number dropped on the [[bunker]] during post-war testing<ref>{{harvnb|Project Ruby|1946|p=214}}</ref>]]

In [[World War II]], the British designer [[Barnes Wallis]], already famous for inventing the [[bouncing bomb]], designed two bombs that would become the conceptual predecessors of modern bunker busters: the five [[tonne]] [[Tallboy bomb|Tallboy]] and the ten tonne [[Grand Slam bomb|Grand Slam]]. These were [[Earth quake bomb|"Earthquake" bombs]]—a concept he had first proposed in 1939.<ref>{{Cite web|title=Earthquake Bombs |publisher= Barnes Wallis Foundation|url=https://www.barneswallisfoundation.co.uk/portfolio/earthquake-bombs/|access-date=2020-11-27|language=en-GB}}</ref> The designs were very aerodynamic, allowing them to exceed the speed of sound as they fell from 22,000&nbsp;ft (6,700&nbsp;m). The tails were designed with offset fins causing the bombs to spin as they fell. Using the same principle as a [[spinning top]], this enabled them to resist being deflected, thereby improving accuracy. They had casings of high grade steel, much stronger than the typical World War II bomb so that they would survive hitting a hardened surface, or penetrate deep into the ground.

Though these bombs might be thought of as "bunker busters" today, the original "earthquake" theory was more complex and subtle than simply penetrating a hardened surface. The earthquake bombs were designed not to strike a target directly, but to impact beside it, penetrate under it, and create a '[[camouflet]]', or large buried cavern, at the same time as delivering a shock wave through the target's foundations. The target then collapses into the hole, no matter how hardened it may be. The bombs had strong casings because they needed to travel through rock rather than reinforced concrete, though they could perform equally well against hardened surfaces. In an attack on the [[Valentin submarine pens|Valentin U-Boat pens]] at [[Farge]], two Grand Slams went through the 15&nbsp;ft (4.5 m) reinforced concrete hardening{{sfn|RAF staff|2005}}—equalling or exceeding the best current penetration specifications.

The British [[Disney bomb|''Disney'' bomb]] (officially "4500 lb [2,000 kg] Concrete piercing/Rocket Assisted Bomb", also known as the "Crab") was a World War II device designed to be used against U-boat pens and other super-hardened targets. Devised by Captain [[Edward Terrell]] [[Royal Navy Volunteer Reserve|RNVR]] of the Admiralty's [[Directorate of Miscellaneous Weapons Development]],{{sfn|Terrell|1958|pp=197–212}} it had a streamlined hardened case and weighed about {{convert|4500|lb|abbr=on}} including the rocket assembly. The actual explosive content was about {{convert|500|lb|kg|abbr=on}}.

For accuracy, the bombs had to be dropped precisely from a pre-determined height (usually {{convert|20000|ft|m|abbr=on}}).<ref name="pol556">{{harvnb|Burakowski|Sala|1960|p=556}}</ref> They would free-fall for around 30&nbsp;seconds until, at {{convert|5000|ft|m|abbr=on}}, the rockets were ignited, causing the tail section to be expelled.<ref name="pol556" /> The rocket burn lasted for three seconds<ref name="ruby18" /> and added {{convert|300|ft/s|m/s|abbr=on}} to the bomb's speed, giving a final impact speed of {{convert|1450|ft/s|m/s mph|abbr=on}},<ref name="ruby18">{{harvnb|Project Ruby|1946|p=18}}</ref> approximately [[Mach number|Mach]] 1.29.<ref group=lower-alpha>Other sources mention a striking speed of {{convert|2400|ft/s|m/s mph|abbr=on}}. ({{harvnb|Johnsen|2003|p=45}}, {{harvnb|Burakowski|Sala|1960|p=556}})</ref> Post-war tests demonstrated that the bombs were able to penetrate a {{convert|14|ft|8|in|m|adj=on}} thick concrete roof,<ref name="ruby23">{{harvnb|Project Ruby|1946|p=23}}</ref> with the predicted (but untested) ability to penetrate {{convert|16|ft|8|in|m}} of concrete.<ref name="ruby23"/>

====United States====
Post war, the US added a form of remote guidance to the Tallboy to create the ''[[Tarzon]]'', a {{convert|12,000|lb|kg|abbr=on}} bomb deployed in the [[Korean War]] against an underground command center near [[Kanggye]].