Obviously they'll get him afterwards but the beauty of a surprise attack is that it's a surprise. Ambushes always work to a degree

Ironically the reason why in Warcraft the only time/war that the Horde won was the first, where they showed up from another world by surprise and raided outlying farms before sacking a city. Everything that came after turned out to be a disaster for them including several wars they lost, two civil wars, and multiple leaders dying or leaving constantly.