One who gives protection from harm is called kshatriya. ... The kshatriyas are specially trained for challenging and killing because religious violence is sometimes a necessary factor. ... In the religious law books it is stated: ‘In the battlefield, a king or kshatriya, while fighting another king envious of him, is eligible for achieving the heavenly planets after death, as the brahmanas also attain the heavenly planets by sacrificing animals in the sacrificial fire.’ Therefore, killing on the battlefield on religious principles and killing animals in the sacrificial fire are not at all considered to be acts of violence, because everyone is benefited by the religious principles involved
Swami Prabhupada, Bhagavad-Gita as It Is
Swami Prabhupada, Bhagavad-Gita as It Is