XCOM: Enemy Unknown built on the premise of a modern day UFO agency designed to hunt down and eliminate alien threats. But a new video for The Bureau: XCOM Declassified delves into how developer 2K Marin envisioned the creation of that clandestine organization back in the 1960s.

The trailer, narrated by 2K Marin's director of product development Alyssa Finley, also discusses protagonist William Carter, and how he controls his team in tactical combat using a mechanic known as battle focus. Emphasis will be on skill and tactics and not running in with guns blazing, Finley says.

Our first look at the game gave us the impression of Mass Effect set in the 1960s. But players will be able to figure it out for themselves when it hits PC, Xbox 360 and PlayStation 3 on August 20.