In the Mahabharata war, the Kauravas form the chakravyuha, a battle formation. Arjuna’s young son Abhimanyu says: “I have been taught by my father the method of (penetrating and) smiting this kind of array. I shall not be able, however, to come out if any kind of danger overtakes me.”
A later folk version adds that Abhimanyu heard how to enter the formation while still in his mother’s womb. He never heard how to come out, and this incomplete knowledge led to his death.