[Update - 10:00am CST] In addition to the debut trailer and release date, Epic has confirmed that Gears of War 3 will offer four-player co-op throughout its main story campaign.

[Original] Hot on the heels of Gears of War 3's official announcement--and a little longer after its accidental announcement--publisher Microsoft has released a grim first trailer for Epic's shooter to the world with a selection of still frames and named a firm release date.

"With the last human city destroyed and the remaining survivors stranded, time is running out for Marcus and his comrades as they fight to save the human race from the jaws of extinction," an announcement from Microsoft explains, as Delta Squad face not only the returning Locust Horde but tentacled new foes the Lambent.

"When we released 'Gears of War' more than three years ago, we set out to tell the world an unforgettable story of bravery and sacrifice in the face of insurmountable odds, and a year from now, players will get the chance to experience the final chapter in the story of Marcus Fenix and his companions in Delta Squad," said design director Cliff Bleszinski.

Gears of War 3 will be released exclusively for Xbox 360 on April 5, 2011, in North America and Asia, on April 7 in Japan then April 8 in Europe and all other countries.