Included under the terms of the agreement, Activision has acquired the publishing rights to Day of Defeat, a multiplayer game powered by Valve's Half-Life technology. Day of Defeat is scheduled for release this May.

"Valve has a proven track record of creating ground-breaking games with worldwide appeal," said Larry Goldberg, executive vice president of Activision Worldwide Studios. "We share with Valve the common goal of delivering the best games possible and with the upcoming launch of Day of Defeat we look forward to kicking-off a strong and successful partnership."

"Activision has been a pioneering games publisher since the days of the Atari 2600, and the company has never been more influential than it is today," said Gabe Newell, co-founder and managing director of Valve. "It's an honor to enter this new partnership and have the opportunity to take Day of Defeat, an ambitious product born of the MOD community, to gamers around the world in a great retail offering."