- "With rising cruelty and brutal intent from the weasels of Darkheather, Matriarch Gwendolyn is forced to throw the Mouse Guard into open war to defend the sanctity of every mouse life in the Territories in a bitter winter. Familiar Guardmice Kenzie, Saxon, Rand, Midnight, and Loukas are no longer used for patrol, but as soldiers needing to end their enemy’s ability to make war."
- ―Description, Mouse Guard website.
Mouse Guard: Weasel War of 1149 is the working title for the upcoming fourth entry in the main Mouse Guard series. Set in 1149, the book will cover the Mouse Guard's war against an invasive force of Darkheather weasels.
Mouse Guard author and illustrator David Petersen has begun working on the story, but, as of April 2020, there is no release date set for the first issue.
As of April 2020, the Weasel War of 1149 is scheduled to be divided into eight issues — the longest Mouse Guard graphic novel to date — which will be divided into two hardcover volumes.