Designed in the last decades of the Age of War before the formation of the Star League, the Atreus-class served as the backbone of several Free Worlds naval battlegroups until it was lost in the First Succession War. Although considerably less in mass than the Star League and Clan vessels that would follow, the 1.1 million ton vessels were among the largest in existence when they first appeared in 2552, a clear demonstration of the League's economic and martial strength. The design easily matched those fielded by the Lyran Commonwealth, Capellan Confederation and Terran Hegemony, and a succession of field upgrades ensured the design's continued dominance. Its closest rival was the Hegemony's aging Monsoon-class, which utilized a succession of high-tech upgrades in a vain attempt to match the Atreus' performance, the Farragut (which the Atreus could still outrun and outgun) and Texas (which returned naval dominance to the Hegemony).
         Well armored and agile for its mass (capable of a sustained 1.5Gs and 2.5G sprints) and with impressive close-in weapons, the Atreus was an excellent all-round performer. Naval autocannons provided formidable close in and mid-range firepower, while naval lasers and naval PPCs provided devastating long-range capability. However, the Atreus's armament demonstrated it's greatest weakness-the magazines for each of the main cannon contained only ten rounds of ammunition per gun. This required the vessel to win its engagements quickly or else rely on its much weaker energy armament. The Atreus also carried limited anti-fighter and anti-missile defenses, relying instead on its four squadrons of fighters to screen it from small enemy craft.
         Unfortunately, while its weaponry and technical systems received considerable updates by the FWLM, the Atreus's barracks-style quarters were largely neglected. Crews did not like serving onboard the Atreus, whose cramped corridors and common spaces provided little opportunity for privacy. The only single-occupancy cabins aboard the Atreus were those of the captain, first officer and the commander of the fighter squadrons (known as the Commander Air Group or CAG).
         The last of these formidable vessels entered service in 2681. A few were lost in skirmishes with the League's neighbors and the Reunification War, but almost two-thirds remained in League service when the Star League collapsed. The ship played a vital role in the League's gains in the First Succession War. All Atreus-class ships remaining were lost in that conflict, the last falling victim to Lyran fighters in 2809.