Genghis Khan tactic
I believe the answer is:
siege
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">genghis khan tactic</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for siege that I've seen before include "Besetting" , "Military operation surrounding a town" , "Offensive encirclement" , "Persistent attempt to gain" , "Military encirclement" .)