Time On Target

Time On Target is the co-ordination of artillery fire by many weapons so that all the munitions arrive at the target at precisely the same time. The military standard is + or - three seconds from the prescribed time of impact. In terms of place, the historical standard was for the impact to occur within 1 circular error probable

Circular error probable

In the military science of ballistics, circular error probable is an intuitive measure of a weapon system's accuracy...

 (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.
As Field Artillery encompassed Fire Support, TOT also encompassed all delivery systems—close air support, naval gunfire, attack aviation, and direct fire ground systems. Therefore, TOT now designates the exact time and place where all weapon systems now focus firepower to destroy or neutralize the enemy target.
Time on target or (TOT) is an estimate of when an artillery bombardment

Artillery

Artillery is a military combat Arm that employs weapons capable of discharging large projectiles in combat. They are generally capable of adding considerable fire power to the military capability of an armed force...

 or an airstrike

Airstrike

An air strike is a military strike by air forces or other military aviation assets against either a suspected or a confirmed enemy ground position. Air strikes are commonly delivered from aircraft such as bombers, ground attack aircraft, strike fighters, and Attack helicopters. Weapons used in an...

 will strike an intended target area. It was first developed by the US Army shortly before World War II

World War II

World War II, or the Second World War , was a global military conflict which involved a majority of the world's nations, including all great powers, organized into two opposing military alliances: the Allies and the Axis...

 to help improve the effectiveness of artillery firepower.

Allied artillery units were often trained to fire their guns in a precise order, so that all shells would hit a target at the same time, delivering the maximum possible damage. This is given to the soldier or officer who requests a bombardment or an air strike.

A shorter TOT usually means a smaller or less important target, and the deployment of less artillery or aircraft. A longer TOT means that the target is large or extremely important, so preparations for a massive bombardment or air strike will take longer.

TOT is important when bombarding enemy targets as it maximizes the destructive force of the bombardment. It was found during the World War One that most of the casualties in an artillery bombardment occur within the first few seconds. After that enemy troops have gone prone and/or sought cover. This dramatically lessens the casualties from shrapnel

Fragmentation (weaponry)

Fragmentation is the process by which the casing of an artillery shell, bomb, grenade, etc. is shattered by the detonating high explosive filling. The correct technical terminology for these casing pieces is fragments , although shards or splinters can be used for non-preformed fragments...

or high explosive blast.

During the first few seconds however troops may be in the open and may not be prone. When multiple artillery units are firing it is important to coordinate the TOT so that all units participating have their rounds land in the target area at exactly the same time as late arriving rounds do proportionally far less damage than the initial ones. The TOT calculations thus include distances of participating units and the speed (muzzle velocity) of projectiles involved.