In the terminology of the armed forces, encirclement is a term for the situation when a military force is surrounded by enemy forces and isolated. Since it cannot receive supplies or reinforcements, this situation is highly dangerous for the encircled force. On the tactical level, the units in the force trapped in the encirclement can be subject to an attack from several or all sides. Because the force cannot retreat, it has only three alternatives; break out of the encirclement, fight to the death, or surrender.
In order to break out of an encirclement, the trapped unit must have a experienced good commander who can calmly assess the situation and the strength of the enemy forces, accurately ascertaining the enemy weak point through which to hammer their way out, using artillery, armor vehicles, or mortar fire. A good example of a break out is the Kovel encirclement in 1944, when a German unit got trapped in a Red Army encirclement in the Ukraine.
Encirclement has been used throughout the centuries by military leaders, including famous generals such as Alexander the Great, Hannibal, Sun Tzu, Wallenstein, Napoleon I, Heinz Guderian, von Rundstedt, Zhukov, and Patton. Sun Tzu suggests that an army should not be completely encircled, but should be given some room for escape, in order to prevent that ‘encircled’ army’s men lifting their morale and fighting till the death –- a more optimal situation would be them considering the possibility of a retreat.
[...] the Soviet Union, from August 23 to September 26, 1941. The Battle of Kiev resulted in the largest encirclement of troops in history in which more than 665,000 Soviet troops were trapped by the German [...]