This manual of spiritual warfare, written in the XV century by one of the greatest Russian church fathers and Orthodox Christian spiritual warriors of the time -- Saint Nilus of Sora, provides a lot of extremely valuable insights on the essence of spiritual warfare, as well as the concrete techniques on how to wage it and how to always be victorious in it. This classic text is considered to be part of the Easter Orthodox Christian tradition. In this new translation, a great care has been taken to preserve both the spirit and the precise meaning of the original text as well as its unique literary style. The word choices and phrasal compositions were made to closely match the word meanings and phrasal structures of the original document whenever this did not compromise the readability of the English text and did not obscure the meaning, so that the translation would remain as close to the original as possible.