Having a broad goal doesn't mean you're limited to only that one. Short term plans are means to an end- steps that you take towards accomplishing the nonspecific end. "Protect the village" can become "stop the droids from kidnapping people", which filters down into "patrol the streets", "recruit more members", "train everyone to defend themselves".

Having only smaller goals makes a group indecisive and aimless. You accomplish more, but you're not working towards anything.