出其不意，攻其不备

出其不意，攻其不備
chūqíbùyì,gōngqíbùbèi
to catch an enemy off guard with a surprise attack (idiom, from Sunzi's "The Art of War" 孙子兵法 Sūnzǐ Bīngfǎ)

CEDICT

Entry Composition

1 出其不意 chūqíbùyì to do sth when least expected (idiom); to catch sb off guard
2 攻其不备 gōngqíbùbèi see 出其不意，出其不意，攻其不备 chūqíbùyì,gōngqíbùbèi