Because the Buggers have more than one world, thought Bean. Of course they do. They found Earth and expected to turn it into yet another colony, just as they've done before.
We have more than one fleet. One for each Formic world.
And the reason they can learn from battle to battle is because they, too, have faster-than-light communication across interstellar space.
All of Bean's guesses were confirmed. He also knew the secret behind these tests. Mazer Rackham wasn't commanding a simulated Bugger fleet. It was a real battle, and Rackham's only function was to watch how it flowed and then coach Ender afterward on what the enemy strategies meant and how to counter them in future.
That was why they were giving most of their commands orally. They were being transmitted to real crews of real ships who followed their orders and fought real battles. Any ship we lose, thought Bean, means that grown men and women have died. Any carelessness on our part takes lives. Yet they don't tell us this precisely because we can't afford to be burdened with that knowledge. In wartime, commanders have always had to learn the concept of "acceptable losses." But those who keep their humanity never really accept the idea of acceptability, Bean understood that. It gnaws at them. So they protect us child-soldiers by keeping us convinced that it's only games and tests.
Therefore I can't let on to anyone that I do know. Therefore I must accept the losses without a word, without a visible qualm. I must try to block out of my mind the people who will die from our boldness, whose sacrifice is not of a mere counter in a game, but of their lives.
The "tests" came every few days, and each battle lasted longer. Alai joked that they ought to be fitted with diapers so they didn't have to be distracted when their bladder got full during a battle. Next day, they were fitted out with catheters. It was Crazy Tom who put a stop to that. "Come on, just get us a jar to pee in. We can't play this game with something hanging off our dicks." Jars it was, after that. Bean never heard of anyone using one, though. And though he wondered what they provided for Petra, no one ever had the courage to brave her wrath by asking.
Bean began to notice some of Ender's mistakes pretty early on. For one thing, Ender was relying too much on Petra. She always got command of the core force, watching a hundred different things at once, so that Ender could concentrate on the feints, the ploys, the tricks. Couldn't Ender see that Petra, a perfectionist, was getting eaten alive by guilt and shame over every mistake she made? He was so good with people, and yet he seemed to think she was really tough, instead of realizing that toughness was an act she put on to hide her intense anxiety. Every mistake weighed on her. She wasn't sleeping well, and it showed up as she got more and more fatigued during battles.
But then, maybe the reason Ender didn't realize what he was doing to her was that he, too, was tired. So were all of them. Fading a little under the pressure, and sometimes a lot. Getting more fatigued, more error-prone as the tests got harder, as the odds got longer.
Because the battles were harder with each new "test," Ender was forced to leave more and more decisions up to others. Instead of smoothly carrying out Ender's detailed commands, the squadron leaders had more and more of the battle to carry on their own shoulders. For long sequences, Ender was too busy in one part of the battle to give new orders in another. The squadron leaders who were affected began to use crosstalk to determine their tactics until Ender noticed them again. And Bean was grateful to find that, while Ender never gave him the interesting assignments, some of the others talked to him when Ender's attention was elsewhere. Crazy Tom and Hot Soup came up with their own plans, but they routinely ran them past Bean. And since, in each battle, he was spending half his attention observing and analyzing Ender's plan, Bean was able to tell them, with pretty good accuracy, what they should do to help make the overall plan work out. Now and then Ender praised Tom or Soup for decisions that came from Bean's advice. It was the closest