Shadow of the Hegemon

Shadow of the Hegemon is the second book in Orson Scott Card's Ender's Shadow series, which starts with a sequel to Ender's Game told from mostly from the point of view of Bean, a largely peripheral character in Ender's Shadow. In Shadow of the Hegemon the Battle School graduates, except for Ender, return to their homes on Earth. Ender's brother Peter, acting as his online pseudonym Locke (a conscious nod to John Locke), has caused Ender to return to Earth only to pick up Valentine before leaving for another planet. Shortly after the rest of the Battle School graduates return, they are kidnapped to be used as strategists in an oncoming world war.

warning: Wikipedia contains spoilers

The person behind the kidnappings, Achilles--the sociopath Bean foiled in the previous novel--attempts to kill Bean and his family, but they avoid the attempt. After Bean discovers an encoded message, he works to rescue Petra while helping Peter come to power under his own name so he can eventually be appointed Hegemon and work against Achilles.

Achilles, in India, plans an invasion of Burma and then Thailand. Most of the kidnapped Battle School graduates, as well as some that came to Achilles of their own accord, arrange brute force attacks involving long supply lines. Petra arranges a different plan, expecting it never to be used because India could not afford to divert enough of an army from its border with Pakistan to make the attacks as Achilles plans. What she does not know is that Achilles plans to arrange a nonagression pact with Pakistan, leaving the troops free to leave the border. He takes her along as a hostage to the meeting, and deftly arranges just such a treaty. Petra, crestfallen, sabotages the rest of her work while waiting for Bean to get the encoded message she sent and arrange a rescue.

Nonetheless her plan is not used, but for a different reason than Petra expects: Achilles is secretly working for China, and has arranged to have China attack India after India puts the bulk of its forces along the border of Thailand. At that point, Achilles plans to leave India for China, and continue his efforts towards world domination.