The Halcyon-class light cruiser (Pronounced ˈhalsēən) (known as Human Attack Ship class C-II by the Covenant) was a United Nations Space Command cruiser starship classification designed by Dr. Robert McLees in 2510, with a Hull classification symbol of SCS. Their service lives were short due to a unique hull design that was costly both to construct and to maintain, lack of speed, poor armament, and concerns about their tactical viability. They were subsequently replaced by the Marathon-class heavy cruiser. Despite the inherent disadvantages of the design, if upgraded appropriately and handled well, they could be among the most effective, and likely the most expensive, ships in the UNSC Navy.