Commentarii de Bello Gallico (English: Commentaries on the Gallic War) is Julius Caesar's firsthand account of the Gallic Wars, written as a third-person narrative. In it Caesar describes the battles and intrigues that took place in the nine years he spent fighting local armies in Gaul that opposed Roman domination.
The work has been a mainstay in the teaching of Latin to schoolchildren, its simple, direct prose lending itself to that purpose. It begins with the frequently quoted phrase "Gallia est omnis divisa in partes tres", sometimes quoted as "Omnia Gallia in tres partes divisa est", meaning "All Gaul is divided into three parts". (Summary from Wikipedia)