Agni Purana (Jyotisha Selections) · by Vyasa
Chapter 5 · Omens
शकुनानि
शत्रोर्वा व्यसने यायाद्दैवाद्यैः पीडितं परम् ।भूकम्पो यां दिशं याति यां च केतुर्व्यदूषयत् ॥ ३ ॥
In the full Agni Purana this is chapter 228, verse 3.
One may march when the enemy is in trouble. So too when he is badly hit by fate and the like. March toward the direction an earthquake moves to. Also toward the direction Ketu has spoiled.
Simple meaning: March when the enemy is in trouble, or toward a direction hit by an earthquake or Ketu.
विद्विष्टनाशकं सैन्यं संभूतान्तःप्रकोपनम् ।
March when your army is strong, the enemy faces revolt, and twitches and dreams are good.
निमित्ते शकुने धन्ये जाते शत्रुपुरं व्रजेत् ।
On good omens, go against the enemy city. In the rains, send an army of foot soldiers and elephants.
सेना पदातिबहुला शत्रूञ्जयति सर्वदा ।
An army strong in foot soldiers wins. A twitch on the right side of the body is good.