Tā xuǎnzé zài duìshǒu fēnxīn de shíhou gōng qí bù bèi.
He chose to strike his opponent off guard when they were distracted.
Tips
history
From 《孙子·计篇》 ('Sun Tzu, chapter on Calculations'): 攻其无备，出其不意 ('attack where they are unprepared; appear where you are not expected'). The idiom is half of one of Sun Tzu's most-quoted lines on surprise.
usage
Often paired with 出其不意 (chūqíbùyì, 'take by surprise') as a fixed couplet — they reinforce the same idea of catching the opponent off guard.
