King Wei's Inquiry
必攻不守，兵之急者也。
Attack the undefended—this is the urgent priority of the army.
威王问于孙膑曰：'用兵之道，何为先？'孙膑对曰：'必攻不守，兵之急者也。'
以寡击众者，利也；以弱胜强者，势也。
齐威王问孙膑："用兵之道，什么最重要？"孙膑回答："专攻敌人不设防之处，这是用兵最紧迫的原则。"以少量兵力击败众多敌军，靠的是有利的态势；以弱胜强，靠的是造势。
King Wei asked Sun Bin: "What is the most important principle of warfare?" Sun Bin replied: "Attack the undefended—this is the urgent priority of the army." Defeating a larger army with a smaller one relies on advantage; overcoming a stronger enemy with a weaker one relies on momentum.
必攻不守（专攻敌人薄弱要害）；以寡击众、以弱胜强
Attack the undefended (focus on the enemy's weak and vital points); defeat the many with the few and the strong with the weak.
"必攻不守"是孙膑兵法的核心命题，比孙子"避实击虚"更进一步——不仅要避开敌人的强点，更要主动寻找并攻击其不设防的要害。这是一种积极主动的进攻哲学。
Compare to Michael Porter's "Blue Ocean Strategy" — creating uncontested market space. Compare to Blitzkrieg doctrine.
孙膑利用减灶之计诱敌深入，在马陵道设伏，万弩齐发，大败魏军。
Sun Bin used a ruse of reducing cooking stoves to lure the enemy deep into Maling Pass, where thousands of crossbows fired in ambush, devastating the Wei army.
美军避开日军主力舰队，集中攻击其航母编队这一致命弱点。
The US Navy bypassed Japan's main fleet and concentrated its attack on the carrier groups — the fatal weak point.
小米避开传统渠道，以互联网直销攻其不设防的线上市场。
Xiaomi bypassed traditional retail channels and attacked the undefended online market through direct internet sales.