ENDER'S GAME

library in the fleet. Nothing more significant than that."

Bean shrugged.

"You spent two hours on Vauban."

"So what? I spent as long on Frederick the Great, and I don't think we're doing field drills, either, or bayoneting anyone who breaks ranks during a march into fire."

"You didn't actually read Vauban, did you," said Dimak. "So I want to know what you *were* doing."

"I *was* reading Vauban."

"You think we don't know how fast you read?"

"And *thinking* about Vauban?"

"All right then, what were you thinking?"

"Like you said. About how it applies to war in space." Buy some time here. What *does* Vauban have to do with war in space?

"I'm waiting," said Dimak. "Give me the insights that occupied you for two hours just yesterday."

"Well of course fortifications are impossible in space," said Bean.

"In the traditional sense, that is. But there are things you can do.

Like his mini-fortresses, where you leave a sallying force outside the main fortification. You can station squads of ships to intercept raiders. And there are barriers you can put up. Mines. Fields of flotsam to cause collisions with fast-moving ships, holing them. That sort of thing."

Dimak nodded, but said nothing.

Bean was beginning to warm to the discussion. "The real problem is that unlike Vauban, we have only one strong point worth defending -Earth. And 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."