The First Great War (known alternatively as Great War I, the Human-Covenant War, or the War of Vain Attrition) was an interstellar, multi-decade war beginning in 2525 and closing with the Great Schism's end in 2554. It took the lives of more than one hundred billion sentient beings; as such, it would be the most brutal conflict for any of the participating species at the time of its happening.