Battle of Actium
From Halopedia, the Halo wiki
In May 2545, a Covenant armada invaded Actium. By May 10, Colonel Akono Menteith, whom had assumed command of the UNSC Army's 53rd Armored Division, gave a rousing speech to the roughly twelve-thousand surviving UNSC soldiers. Later that month, he led the remnants of the division deep into Covenant-held territory in order to destroy three of the largest Covenant staging areas on record; the 53rd did so with the aid of a pair of HAVOK tactical nuclear weapons, though they suffered heavy attrition.
Within the month, the 53rd Armored Division was annihilated. Actium fell to the Covenant and was presumably glassed. Colonel Menteith's speech became legendary throughout the colonies as a symbol of human resistance against the Covenant.
The battle shares its name with a real-world engagement that occurred in 31 BC. The historical Battle of Actium is often considered a crucial step in the transition of the Roman Republic into the Empire.