Ubisoft has announced that the For Honor closed beta will begin on January 26 and run until January 29. The start of the closed beta will also mark the kickoff of the War of the Factions, the eternal, multiplatform clash between the Vikings, the Samurai, and the Knights which you probably don't remember from high school history.
The War of the Factions will track all players during the closed beta, rewarding those who fight well, with bonuses for members of the winning faction. (Remember, you can fight for any faction at any time, but pledge your allegiance—and your performance in battle—to just one of them.)
Players who take part in the closed beta, regardless of how well (or otherwise) they perform will also be given the "Emblems of Old," representing "the undying bravery and resilience of For Honor’s mightiest heroes," which can be applied to in-game weapons and armor. Those, and all other rewards, will carry over into the full game.
Specific start and end times for the closed beta haven't been announced, but you can sign up to get in on the action at forhonorgame.com/war.