Lord Brocktree (Redwall, #13)

The young haremaid Dotti and the badger-warrior Lord Brocktree—unlikely comrades—set out for Salamandastron together, only to discover the legendary mountain has been captured by the wildcat Ungatt Trunn and his Blue Hordes. To face them, the two must rally an army—hares and otters, shrews and moles, mice and squirrels—and execute a plan that makes up in cleverness what it lacks in force.