Best defense is offence.

进攻是最好的防御。/先下手为强。

【世博精解】

Defense, the American spelling of defence, it means the act of protecting something or someone from attack. 防御；防卫；防护。Air defense防空/ frontier defense边防/ defense and offence strategies and tactics防守和进攻的战略战术。

Offence, the act of attacking, 进攻，攻击。Weapons of offense进攻性武器。

这个谚语从字面上解释是“最好的防御就是进攻”，意为“进攻是最好的防御”或“先下手为强”。