the enemy is not limited to a primary direction of approach. He could come from anywhere. From anywhere all at once. So we run into the classic problem of defense, cubed. The farther out you deploy your defenses, the more of them you have to have, and if your resources are limited, you soon have more fortifications than you can man. What good are bases on moons Jupiter or Saturn or Neptune, when the enemy doesn't even have to come in on the plane of the ecliptic? He can bypass all our fortifications. The way Nimitz and MacArthur used two-dimensional island-hopping against the defense in depth of the Japanese in World War II. Only our enemy can work in three dimensions. Therefore we cannot possibly maintain defense in depth. Our only defense is early detection and a single massed force."
Dimak nodded slowly. His face showed no expression. "Go on."
Go on? That wasn't enough to explain two hours of reading? "Well, so I thought that even that was a recipe for disaster, because the enemy is free to divide his forces. So even if we intercept and defeat ninety-nine of a hundred attacking squadrons, he only has to get one squadron through to cause terrible devastation on Earth. We saw how much territory a single ship could scour when they first showed up and started burning over China. Get ten ships to Earth for a single day - and if they spread us out enough, they'd have a lot more than a day! - and they could wipe out most of our main population centers. All our eggs are in that one basket."
"And all this you got from Vauban," said Dimak.
Finally. That was apparently enough to satisfy him. "From thinking about Vauban, and how much harder our defensive problem is."
"So," said Dimak, "what's your solution?"
Solution? What did Dimak think Bean was? I'm thinking about how to get control of the situation here in Battle School, not how to save the world! "I don't think there is a solution," said Bean, buying time again. But then, having said it, he began to believe it. "There's no point in trying to defend Earth at all. In fact, unless they have some defensive device we don't know about, like some way of putting an invisible shield around a planet or something, the enemy is just as vulnerable. So the only strategy that makes any sense at all is an all-out attack. To send our fleet against their home world and destroy it."
"What if our fleets pass in the night?" asked Dimak. "We destroy each other's worlds and all we have left are ships?"
"No," said Bean, his mind racing. "Not if we sent out a fleet immediately after the Second Bugger War. After Mazer Rackham's strike force defeated them, it would take time for word of their defeat to come back to them. So we build a fleet as quickly as possible and launch it against their home world immediately. That way the news of their defeat reaches them at the same time as our devastating counterattack."
Dimak closed his eyes. "Now you tell us."
"No," said Bean, as it dawned on him that he was right about everything. "That fleet was already sent. Before anybody on this station was born, that fleet was launched."
"Interesting theory," said Dimak. "Of course you're wrong on every point."
"No I'm not," said Bean. He knew he wasn't wrong, because Dimak's air of calm was not holding. Sweat was standing out on his forehead. Bean had hit on something really important here, and Dimak knew it.
"I mean your theory is right, about the difficulty of defense in space. But hard as it is, we still have to do it, and that's why you're here. As to some fleet we supposedly launched - the Second Bugger War exhausted humanity's resources, Bean. It's taken us this long to get a reasonable-sized fleet again. And to get better weaponry for the next battle. If you learned anything from Vauban, you should have learned that you can't build more than your people have resources to support. Besides which, you're assuming we know where the enemy's home world is. But your analysis is good insofar as you've identified the magnitude of the problem we face."
Dimak got up from the bunk. "It's nice to know that your study time isn't completely wasted on breaking into the computer system," he said.