Arthashastra
यद् वा परस्य सारिष्ठं तद् द्वि गुण सारेण अभिहन्यात् ॥
He should increase the numerical strength of that constituent of the army which is physically weak.
english translation
yad vA parasya sAriSThaM tad dvi guNa sAreNa abhihanyAt ॥
hk transliteration by Sanscript