The Valkyria Chronicles series takes place in an alternate universe version of Europe called Europa. The neutral nation of Gallia, home of the heroes of the game, comes under attack by a larger faction seeking to secure resources as part of a larger war.
Valkyria Chronicles is, like Nintendo's Fire Emblem series, a tactical role-playing game, in which the player and opposing forces take turns moving characters around a map. What distinguishes this series is the inclusion of action elements, such as manually aiming characters' rifles at opponents.
The original Valkyria Chronicles was released in April 2008 in Japan and at the end of the year elsewhere.
Valkyria Chronicles 2 was released just under two years later, in 2010. Taking place some time after the events of the original game, it focuses on preventing an ethnic cleansing by a rogue element.
Valkyria Chronicles 3 was released in 2011. It was a side-story to the events of the original game, focusing on a different group of characters and having a much darker tone.
Valkyria Chronicles is one of Sega's better received recent new franchises. All three games in the series have received great reviews, with the original being considered on of the great Sega exclusives of 2008. The series has also sold millions of games, making it a notable, if somewhat niche, franchise for the company, similar to how Fire Emblem is for Nintendo.