Art of War [[谋攻第三 | 其次伐兵 ]]

故用兵之法，十则围之，五则攻之，倍则分之，敌则能战之，少则能逃之，不若则能避之。
故小敌之坚，大敌之擒也。

It is the rule in war,
if our forces are ten to the enemy's one, to surround him;
if five to one, to attack him;
if twice as numerous, to divide our army into two.
If equally matched, we can offer battle;
if slightly inferior in numbers, we can avoid the enemy;
if quite unequal in every way, we can flee from him.

Hence, though an obstinate fight may be made by a small force, in the end it must be captured by the larger force.