When are they supposed to be planning, exactly? That's the problem with your argument: There's no time for them to sit down and figure out a step by step plan. The invasion is already underway and there's no time to waste. If they're going to do anything, it has to be right now and they are going to have to improvise on the way before it's impossible for them to do anything at all-which it nearly was; if they'd been delayed any more than they had the Queen and the rest would have been sitting in prison camps. You're assuming that somehow they could have created time to come up with a plan. They had no such time available to them.