casus beli
A justification of war between one nation and another nation over a valid reason
I have a valid Casus Beli against the nation of Thisisanexampleia, with the reason being that they put pineapple on my pizza
or, in a more serious way,
I declare war on the nation of Ukraine for an armed border conflict that caused ten Russian soldiers on the border to pass away
or, in a more serious way,
I declare war on the nation of Ukraine for an armed border conflict that caused ten Russian soldiers on the border to pass away