Complex sentence: At this point, Smiley decides to "shake Ko's tree," i.e. let him realize he is being exposed by the investigation, to provoke Ko into taking action which will advance the operation.
Split into simpler sentences: At this point, Smiley decides to "shake Ko's tree," i.e. let him realize he is being exposed by the investigation. This will provoke Ko into taking action which will advance the operation.