I've noticed recently that in each Redwall book, there are two main character deaths, one during the course of the story and one at the end, with a few exceptions. Here are some examples.
During: Brother Methuselah
End: Abbot Mortimer
During: Queen Warbeak
During: Brother Hal
End: Laterose of Noonvale
End: Finnbarr Galedeep
(*Exceptions: two characters died during the book, instead of one during and one at the end)
These are just a few examples. Now, my next question is: why did Brian Jacques always kill off at least two main characters? I think I might have an answer.
Continuosly throughout the series, we are reminded that killing is bad, and war always leads to killing. Of course, after the war in each book things have improved, for example in Redwall, Matthias was no longer clumsy and had earned the alliance of the Sparrows and Guosim, also he married Cornflower. However, things could have been brighter if Methuselah and Abbot Mortimer had lived. And to quote the Abbot from the TV series (I don't know if he said it in the book), "Fighting always leads to something terrible." Brian continues to remind us of that as he tells how in each story, even though the fighting was justified, something bad came of it. Bad things will always result from fighting.
Now don't think this makes me a pacifist. I just don't think we should invite trouble. It's OK to fight to protect, as the warriors in the Redwall series do. However, in my opinion, starting a war just makes you plain evil.