Ace Combat 5: The Unsung War (エースコンバット5 ジ・アンサング・ウォー, Ēsu Konbatto Faibu Ji Ansangu Wō), released in the PAL region as Ace Combat: Squadron Leader, is a semi-realistic flight combat video game for the PlayStation 2. Like other titles in Namco's Ace Combat series, Ace Combat 5 features gameplay that is a mix between arcade flight and authentic flight simulation. The game was developed by Project Aces, an internal Namco group credited with the development of the Ace Combat series, and was published by Namco in October 2004. A limited number of the games were bundled with the Hori Flightstick 2 accessory.
Ace Combat 5 features more than fifty licensed real-world jet aircraft. Nonetheless, the game's events and locations are set in a fictional world. The game's main campaign is set during a war between the fictitious nations of Osea and Yuktobania. The storyline revolves around the player character "Blaze," an Osean fighter pilot who leads a four-plane unit known as Wardog Squadron. The Unsung War follows this squadron's exploits as they attempt to ward off the Yuktobanian invasion of their homeland and uncover the truth about the war.
Although a majority of the gameplay in Ace Combat 5 remains similar to that of its predecessor, Ace Combat 04: Shattered Skies, several notable additions were made. Among these additions are an arcade mode and the ability for the player to interact with wingmen. The multiplayer mode present in previous titles, however, was scrapped during development. The game has received generally favorable reviews, although critics note that the game is not the "revolutionary step forward for the series" that Shattered Skies was.