Ender's Game Chapter 13: Valentine
The voices have discovered that Locke and Demosthenes, up until this point believed to be two very separate commentators, are Peter and Valentine, respectively. The voices feel, however, that Locke and Demosthenes are still containable.
Valentine and Peter continue their exploits and continue to gain influence. At this point, Graff approaches Valentine to meet Ender, and also that he knows about the Wiggin sibling exploits on Earth. Graff reveals that maybe six people know, and it was going to stay that way, for the time being.
Ender and Valentine meet in person. Ender is on Earth and has been for three months. Valentine again serves as a salve. She fears the hardness and distance in his eyes. However, in the end, she rejuvenates him with compassion, with honesty, and with a little bit of pain. She tells him that it's kill or be killed, and, yes, the weight of the world is on his shoulders. she leaves him and reminds him that, regardless of what the teachers do, she loves him.
Moments later, Ender requests to leave. While leaving, Graff tells Ender that military training intentionally isolates its trainees so that they may think in a way that is strategic, but the soldiers lose sight of why they even fight. A reminder is sometimes useful. Ender resents that Graff forced him to love Earth, and used Valentine. "I may have used Valentine... [but] it only works because what's between you, that's real, that matters." Chapter 13, pg 244
They fly to Command School, on the giant asteroid Eros, together, and Graff becomes Ender's teacher. He tells Ender that Buggers were once like Earth insects and evolved to be the most advanced species around. They communicate mind to mind, the same way humans can communicate instantly (using technology) across long distances in this time period.
Graff is relentless in his teaching of Ender in the ship. We learn of the ansible, Bugger anatomy, and the most important, top secret, fact of Ender's training:. "We are the Third Invasion." Chapter 13, pg 250 The Buggers are not planning to attack Earth, Earth is attacking the Buggers, on every world they live on, including their home world. The first fleets were launched generations ago, and they would arrive in a matter of years.
Since humans and Buggers cannot communicate with humans, it becomes a question of us or them. When faced with that question, Ender chooses humanity.