A bunker buster is a bomb which has been designed to penetrate heavy fortifications, such as underground facilities or reinforced above ground structures. Various versions of the bunker buster have been in use since the Second World War, with a number of militaries designing their own versions. There are also nuclear versions available, although nuclear bunker busters are controversial due to concerns about fallout, contamination, and proliferation of nuclear weapons.
The development of the bunker buster was made possible by the invention of military aircraft which could be used to deliver bombs from great heights. This made bomb deployment significantly safer, and it allowed nations to develop extremely heavy and large bombs which could not have been transported by other means.
Fortified bunkers are built to withstand tanks, bombs, and other types of conventional attacks. They are used to house sensitive equipment, high-profile individuals, and other materials which are considered important for a war effort. By designing a bomb which can penetrate heavily fortified structures, a military can often strike a blow at the nerve center of an enemy government or military.
In order to work effectively, a bunker buster has to be able to penetrate a fortification, and then explode, rather than conventional bombs, which classically explode on impact. The explosion after penetration is timed to deal damage to the core of the bunker, rather than just damaging the exterior, an event which could conceivably be survivable for many bunkers.
To accomplish this goal, a bunker buster is extremely heavy, and narrow for its size. This allows the weapon to build up speed once it is deployed from an aircraft, so that it will be able to bury itself inside a structure or underground. Some bunker busters are mounted with rocket engines which propel the bomb, allowing it to pass through very thick fortifications. The fuse may be time delayed, remotely triggered, or linked to the movement of the bomb, causing it to explode once it has penetrate a fortification.
With the development of bunker busters, of course, many nations have increased the levels of their fortifications to make it harder for these specialized bombs to penetrate. This creates a form of arms race, in which militaries are forced to design better bunker busters, and opponents respond by making their fortifications and bunkers even stronger. The technology involved in the construction of fortifications and bunker busters is usually classified, so that enemy nations cannot acquire it and use it to design their own military equipment accordingly.