Ace Combat 5: The Unsung War is a 2004 combat flight simulation video game developed and published by Namco for the PlayStation 2. The game was developed by Project Aces, an internal Namco group credited with the development of the Ace Combat series.
It 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 fictional 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 as they attempt to ward off the Yuktobanian invasion of their homeland and uncover the truth about the war. Unlike its predecessors, Ace Combat 5 does not include a multiplayer mode, as developers did not have enough time to implement one.
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.
Ace Combat 5: The Unsung War is divided into three gamemodes: Campaign, where players progress through story-driven levels; Arcade, which removes most of the story from Campaign mode in favor of gameplay; and Tutorial, which teaches the player the base mechanics. The gameplay in these three modes is largely consistent; players pilot an aircraft and must complete a series of missions that must be completed in the allotted amount of time. Missions feature a wide array of objectives, ranging from destroying all enemy aircraft in a level to protecting a specific target from enemy fire.
The game features over fifty playable aircraft, including military and experimental aircraft licensed from the United States and Europe, in addition to original designs created specifically for the game. The majority of these aircraft are unlocked by progressing through the Campaign mode, while others are unlocked while destroying a certain amount of enemies with a particular craft.

In the Campaign mode, the player can issue orders to computer-controlled ally fighters, a method known as wingman interaction. With this, players can have fighters team up to take down a single target or spread out to cover more ground. Wingmen can be assigned specific aircraft before beginning a mission. Completing missions awards money that can be used to purchase aircraft, while certain missions feature side games like midair refueling.The player's fighter has a limited number of ammunition, especially on harder difficulties. These fighters are also equipped with side weaponry unique to a particular model, such as guided bombs and salvo missiles that can lock onto multiple ground or aerial targets.