स्वसैन्यव्यायामयोग्यं परस्यायोग्यं वर्षति यायात् ॥ कZ_०९.१.३९ ॥
sva-sainya-vyāyāma-yogyaṃ parasya ayogyaṃ varṣati yāyāt
当己方军队适于劳作而敌军不适于劳作时,他应在雨季出征。
Campaign in adverse seasons only if the adverse effects are asymmetric—your preparedness converts a general constraint into a relative advantage.