Short answers, pulled from the story.
Encirclement occurs when a force or target is isolated and surrounded by enemy forces. This situation creates a highly dangerous environment for the encircled group because they cannot receive supplies or reinforcements at the strategic level.
Generals such as Alexander the Great, Hannibal, Julius Caesar, Genghis Khan, Napoleon, Zhukov, Patton, and Soleimani utilized these tactics. These commanders span centuries of military evolution from ancient battles to modern conflicts.
Sun Tzu suggests that an army should not be completely encircled but rather given some room for escape. Allowing retreat prevents the encircled men from fighting to the death and reduces risk to pursuing forces.
The encirclement of the German Sixth Army occurred in 1942 during the Battle of Stalingrad. This event serves as a typical example of double pincer attacks executed by mobile forces.
The Battle of Ai occurred in 1272 BC while the Battle of Thermopylae took place in 480 BC. Hannibal defeated Roman forces at Cannae in 216 BC and the Battle of the Abas happened in 65 BC.