For Brett @ 10:
Just a minor point, from a Latin teacher (and scratch one of us, you’ll find a pedant):

the plural of casus belli (“pretext for war,” “reason for war”) is also casus belli (“reasons for war”), because casus is a 4th declension noun, with a nominative plural in -us (it’s a long u in the plural, but I can’t type long marks here). It’s therefore different from the commoner -us nouns (like alumnus, plural alumni) that belong to the 2nd declension.

You could also talk about casus bellorum (“the reasons for wars”).