Thomas Aquinas, Summa Theologica, Question 40 on War:
http://www.newadvent.org/summa/3040.htm
Francisco di Vitoria on War:
https://en.wikisource.org/wiki/De_Indis_De_Jure_Belli/Part_3
I just finished a course on the History of Medieval Philosophy - and this movie brought up all the questions of these two readings on war.
Please, check your links: The link to the New Advent site (St. Thomas Aquinas) gives me a "404 Error"; the link to the WikiSource site (Francisco di Vitoria) gives a "bad title" error ("The requested page title contains invalid characters: " ".").
EDIT: bump
~~Bayowolf
There's a difference between being frank... and being dick.
Some challenges to the views of Augustine, Walzer, etc:
https://www.theobjectivestandard.com/issues/2006-spring/just-war-theory/