The first known use of poison gas in warfare was by the Spartans in 429 BCE. During a war with the city-state of Athens, the Spartans attempted to capture a fortress at Plataea by burning wood covered in pitch and sulfur to produce a thick, choking smoke. Their purpose was not only to block the defenders' view but also to overcome the defenders with noxious fumes. While this may have been a form of gassing, it was most likely not what is considered "chemical warfare" in the modern sense. There are no descriptions of people being harmed or killed specifically by poisonous fumes, and the use of the tactic at Plataea was not repeated until several centuries later.