Relic Entertainment's Company of Heroes series celebrates its 10th anniversary this year. The first game debuted in September 2006 and the series is now considered one of the biggest and most highly esteemed in the PC RTS space.

To celebrate the anniversary, GameSpot worked with Sega to share some never-before-seen pieces of concept art and other images from the franchise's vaults.

A big change occurred in 2013, when Sega scooped up the franchise and developer Relic from THQ's bankruptcy auction for $26.3 million. Sega is now the dominant player in the RTS genre, as it also owns the Total War series and developer Creative Assembly.

Click "Next Image" to begin the gallery. Each image is captioned by Sega, providing insight and context.