Time on target
Time on target (TOT) is the military co-ordination of artillery fire by many weapons so that all the munitions arrive at the target at roughly the same time. The military standard for coordinating a time-on-target strike is plus or minus three seconds from the prescribed time of impact. In terms of target area, the historical standard was for the impact to occur within one circular error probable (CEP) of the designated target. CEP is the area on and around the target where most of the rounds will impact and therefore cause the maximum damage. The CEP depends on the caliber of the weapon, with larger caliber munitions having greater CEPs or greater damage on the target area. With the advent of "smart" munitions and more accurate firing technology, CEP is now less of a factor in the target area. In terms of time, Time on target may also refer to the period of time that a radar illuminates a target during a scan. It is closely associated with Dwell time. There may be multiple dwell periods within the Time on Target period. Origins
A technique called Time on target was developed by the British Army in North Africa at the end of 1941 and early 1942 particularly for counter-battery fire and other concentrations; it proved very popular. It relied on BBC time signals to enable officers to synchronize their watches to the second. This avoided the use of military radio networks and the possibility of losing surprise, and eliminated the need for additional field telephone networks in the desert. It had been found during World War I that most of the casualties in an artillery bombardment occur within the first few seconds. During those first few seconds, troops may be in the open and may not be prone. After that, enemy troops have gone prone and/or sought cover. This dramatically lessens the casualties from shrapnel or high explosive blast. World War II Allied artillery units were often trained to fire their guns in a precise order, so that all shells would hit a target simultaneously, delivering the maximum possible damage. Notes

See also 
 Multiple Rounds Simultaneous Impact
 Volley fire

Artillery operation
Targeting (warfare)