Prince Petr Ivanovich Bagration (1765-1812) was a general in the Russian army. He was part of the Bagrationi dynasty, who ruled Georgia from the middle ages until the beginning of the nineteenth century. Bagration's talent as a soldier was recognised by Suvorov during the Swiss and Italian campaigns of 1799. He had a series of successes during 1805, including fending off a force five times stronger than his own during the Battle of Hollabrunn (or Schöngrabern), safeguarding the Russian army's retreat.
Franz von Weyrother (1755-1806) was an Austrian general. He studied at a military engineering school before fighting in the Austro-Turkish war of 1787-1791; he was made a knight of the Order of Maria Theresa in 1795. He planned the attack for the Battle of Austerlitz, and is thus largely held responsible for the subsequent defeat of the Austrian and Russian armies.
Tolstoy is quoting from actual extant letters from Napoleon to his commanders. You can read Napoleon's military correspondence (in French) online at the War Times Journal; here is his writing from the eve of the Battle of Austerlitz.