攻其无备

see 出其不意，攻其不備|出其不意，攻其不备[chu1 qi2 bu4 yi4 , gong1 qi2 bu4 bei4]

not to have / no / none / not / to lack / un- / -less

his / her / its / their / that / such / it (refers to sth preceding it)

variant of 備|备[bei4]

to prepare / get ready / to provide or equip

(bound form) to prepare; to equip / (literary) fully; in every possible way

to attack / to accuse / to study