All round defence
All round defence is a defensive posture, usually adopted in times of confusion by all military units from squad
In military terminology, a squad is a small military unit led by a non-commissioned officer that is subordinate to an infantry platoon. In countries following the British Army tradition this organization is referred to as a section...

 up. In a prepared position
Fortifications are military constructions and buildings designed for defence in warfare and military bases. Humans have constructed defensive works for many thousands of years, in a variety of increasingly complex designs...

, all round defence is adopted so that the unit is capable of observing all ground and directing fire
A gun is a muzzle or breech-loaded projectile-firing weapon. There are various definitions depending on the nation and branch of service. A "gun" may be distinguished from other firearms in being a crew-served weapon such as a howitzer or mortar, as opposed to a small arm like a rifle or pistol,...

 onto the observed ground. It is typically used in all static military operations, or in any situation where a small unit would need to regroup (e.g. after an attack).

As well as being a description of a defensive posture, it is also a specific formation. It is made by the unit forming a wide circle around the officer/s and other important members of the unit (radioman, etc.) with a spacing typically of 3-4 metres between each person. In situations with more than one platoon or squad, more than one all round defence will typically be formed about 20 metres away from each other. This formation can also be used in 'mad minute' attacks. It is a useful formation because it allows a full 360o arc of fire, and because everybody is spread out, if the formation is attacked, by direct or indirect fire
Indirect fire
Indirect fire means aiming and firing a projectile in a high trajectory without relying on a direct line of sight between the gun and its target, as in the case of direct fire...

, the formation will minimise casualties.
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