- "We as Guard offer all that we are to protect the sanctity of our species, the freedom of our kin, and the honor of our ancestors. With knowledge, sword, and shield, we do these deeds, never putting a lone mouse above the needs of all, or the desire of self above another. We strive for no less than to serve the greatest good."
- ―The Guard's Oath 
The Mouse Guard is a group of selfless mice that was formed to help the common mice of the Territories survive. Many skills are necessary for the Guard to keep the borders safe: they must find new safeways and paths from village to village, lead shipments of goods from one town to another, and - in case of attack - guard against all evil and harm to their Territories.
The Guard have fought off a large number of threats to the Mouse Territories including defending against the weasels in the Winter War of 1149. As a result, the Territories are no longer as troubled. The day to day dangers exist, but no longer are the Guard soldiers: instead they are escorts, pathfinders, weather watchers, scouts and body-guards for the mice who live among the Territories.
Ranks of the Guard
There are six echelons within the Mouse Guard:
Tenderpaws - The fresh recruits of the Guard. Tenderpaws are generally accepted into the Guard after they pass a particular rite of passage. This rite often varies, and the only Guardmouse ever known to skip this initiation step was Lieam, under the unusual circumstances of the Winter War of 1149.
Guardmice - The foot soldiers of the Guard.
Patrol Guards - Veteran Guardmice responsible for complicated or independent missions.
Patrol Leaders- Patrol Guard who have demonstrated that they can think independently and guide other mice.
Guard Captain - Powerful mice appointed to the highest militaristic rank in the Guard due to their longstanding commitment and exemplary service
Matriarch - The female leader of the Guard, of which only one can be appointed at a time. The Guard's Matriarch has the final word on decisions and is in complete control of the Mouse Guard.
Duties of the Guard
- The Guard never know when they will be needed or where, so the Guard patrol the known paths and visit towns to offer their services. Patrols are meant to survey the Territories and keep the Guard circulating between the settlements. Guardmice often spend more time away from Lockhaven than in it. They live in the open country. They stay for short visits at settlements before moving on. A patrol will normally have a route it follows or an itinerary left at Lockhaven so the gate-watch of Lockhaven can keep tabs on it.
- Weather and growth can make a once passable and safe route unusable. The Guard clears paths for mice and makes them less inviting for predators. There are times when new trails and paths need to be made. The Guard sends out mice to not only make the path, but make sure it meets a standard: paths should provide cover, plenty of places to hide, and access to food and water.
Helping common mice
- It is the Guard’s duty to ensure safe passage from one settlement to another. The journeys can take several days, so the guardmice must keep watch overnight and be able to forage for food if necessary. Most often they’re escorting shipments of goods, but sometimes guardmice will lead mice to other settlements — dignitaries, mice who perform services or just mice wanting to visit another settlement.
- Messages from heads of town, the Guard’s Matriarch or common townsmice need to be delivered. Because there are few means of communication between the settlements, the Guard will carry messages from a town they are leaving to a town they plan on visiting next. They usually do not head to a settlement specifically to deliver a message unless it’s vitally important.
- It falls on the Guard’s shoulders to help out or rescue mice who have gotten into trouble out in the wild. Regular mice are not well-trained enough to be in the open for long, so rescue missions are fairly common.
- Some governors, mayors and councilmice will call on guardmice to act as mediators and arbiters in disputes between their towns.
Maintanence of the Scent Border
- The Scent Border is a rough line across the southwest and northeast borders of the Territories. Along these borders, the Guard pour a specially brewed mixture that simulates the scent wolves and other animals use to mark territory. The sciencemice of Sprucetuck brew an odd concoction to create a scent that the wolves and foxes tend to respect. It is not completely effective, but it works well enough to keep most large predators out of the Territories.
- The Guard completely repours it twice a year and performs minor maintenance throughout the year.
- The Guard must deal with the animals who threaten mice. This can mean hunting predators, killing their young or ruining their burrows. There have been times in the Guard’s past when the Guard declared war on a species.