UbiBlog has an update from the Rainbow Six Siege development team announcing a delay to the upcoming installment in the tactical shooter series. The game was expected in October, but now they say its worldwide release is coming on December 1st, saying the extra time will allow them to make adjustments and improvements based on feedback as well as their own internal testing. A closed beta will precede the release, and this is currently expected to begin on September 24th. Here's more on the setback:

This wasn’t an easy decision, but based on the feedback we’ve received, and based on our own internal tests, we felt there are adjustments and improvements we can make, including improving the co-op experience across all game modes, weapon and gadget balancing, as well as menu and interface navigation. We’re taking a little more time to make these changes, and we think it’s the right call.

The closed beta for Rainbow Six Siege will still start on September 24, 2015 as planned, and the additional time will allow us to further test things like infrastructure and matchmaking. That extra testing and added polish will make for a higher-quality experience at launch.