Your hero might have to take damage back him even if you loose the surround.
Step1
Select all your me lee units and press m and left click to start moving towards your enemies hero.
Step2
Don't stop clicking m and left click either behind or behind/in front of the hero. Wait until half your units are behind the hero and half your units are in front.
Step3
When your units are half in front and behind quickly press m and left click there hero. They should surround there hero if not keep trying.
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