Should the enemy strengthen his van, he will weaken his rear; should he strengthen his rear, he will weaken his van; should he strengthen his left, he will weaken his right; should he strengthen his right, he will weaken his left. If he sends reinforcements everywhere, he will everywhere be weak.

Sun Tzu's The Art of War: Bilingual Edition Complete Chinese and English Text (ed. Tuttle Publishing, 2012) - ISBN: 9781462905126