Normally, elephants are peaceful mammals. They spend their days eating roots, leaves, bark, and other vegetation in their habitat. But, if a female with a calf or a herd of females with calves feel their young are being threatened, they become aggressive.
As a note, the size of a healthy adult elephant discourages most animal predators from attacking it. A predator or pair of predators may try to attack an adult elephant that is elderly or is suffering from an illness. Elephant calves are especially vulnerable to predators like hyenas, crocodiles, and lions.
A herd of female elephants may charge toward a predator and trample it to death to keep it from attacking a calf in the herd.