Arthashastra
यदा वा प्रयातः कर्शयितुम् उच्छेतुं वा शक्नुयाद् अमित्रं तदा यायात् ॥
or whenever one finds it possible to reduce or destroy an enemy by marching against him, then one may undertake a march.
english translation
yadA vA prayAtaH karzayitum ucchetuM vA zaknuyAd amitraM tadA yAyAt ॥
hk transliteration by Sanscript