In its 10-year-run, David Petersen’s anthropomorphic fantasy series Mouse Guard has been a New York Times bestseller and won both the Eisner and Harvey Awards. It’s gained a loyal following for its story of the Mouse Guard, a brave group of rodent soldiers who protect their fellow citizens against all manner of dangers, from weasels to crustaceans. But it’s Petersen’s gorgeous artwork that has been the stand-out, detailed pen and ink illustrations that build a world as charming as it is adventurous. That art is now spotlighted in The Art of Mouse Guard, out this week from Archaia: a behind the scenes look at the history of the book with new sketches and commentary. Along with this exclusive preview, Petersen spoke with PW about the evolution of his art:

PWCW: David, you have some of your earliest sketches in this book and they all seem to be anthropomorphic. What drew you to telling your story with animal characters and did you ever consider telling it with humans?

David Petersen: When I was drawing the earliest versions of these characters, I was still a high school student and not terribly good at drawing humans, even cartoonish ones. But I love talking animal stories, so setting these stories in that framework was never a burden or confinement, it was a reward, to get to follow in a tradition of books and characters I love like Wind in the Willows, Aesop's Fables, Crow & Weasel, Disney's Robin Hood, and Walk Rabbit Walk. If I'd done the stories from Mouse Guard with humans, I don't think they'd work as well. A human having to slay a dragon doesn't have the same danger as a mouse vs. a snake, I think, because dragons aren't real, but we've all seen enough nature films to know exactly how real is the danger of a mouse against a snake. Also, humans don't feel like human characters in stories are particularly vulnerable, but when we see a mouse character, we think of them as tiny and delicate, fragile and incapable of significant deeds. I prefer to tell this story with animals because I think it works better.

PWCW: Aside from the overall beauty of the art I think what sets Mouse Guard apart is the expressiveness of the characters and how it draws you into the story. Do you think about character design ahead of time? Is there a process you use for putting that level of emotion into the art?

David Petersen: Because the characters are mostly all mice, and I don't give them cartoon brows or facial features, I have to get their emotions across through body language and subtle eye shapes. I remembered what actor Warwick Davis said about seeing his dog tilt its head to various degrees to convey emotion and understanding, so that when he was in the Ewok suit as Wicket—with no part of his face showing—he used his shoulders and the angle of his head to get the emotions through. I tend to draw all the characters about the same other than subtle differences between their clothes and any nicks or missing limbs or injuries, so the only differences in character design are there to help inform what the mouse may have already been through, or how they treat their gear. The place I do most of my ongoing visual development is in trying to make different locations interesting visually and from a world-building perspective.

PWCW: Is there anything you know now that you wish you'd known when you started Mouse Guard?

Petersen: Well, I draw better now than I did then (a result of all that work) and I could write up a list of things I wish I could change, but that would amount to "special editioning" my past books, which I don't think is helpful. I would like to be able to tell myself to enjoy the process more. I recall a lot of stress producing each issue and collection, and still do. I don't know if that will ever go away, but I should remind myself when I'm in the thick of it how much fun it all is.

PWCW: What do you hope that readers get out of this book?

Petersen: That it's all a process. That it develops over time by doing it. That you have to come up with your own tricks to produce your best work. And that your best work is only your best right now if you are doing it right and still learning as an artist and storyteller. I was nervous about the material we were unearthing for the Art of Mouse Guard book, and kept feeling that the early chapters were not going to be interesting and didn't have good enough material for inclusion. But after a few passes I saw that each chapter got closer and closer to my idea of what Mouse Guard is–both on the page and behind the scenes. Seeing over a decade of growth archived and arranged, I understood that while this is a book for Mouse Guard fans about Mouse Guard, it's almost more about growth.