off the top of my head, I'd start thinking about talking about the different ways people can deal with conflict (aggressive methods/passive or peaceful methods) and say something solid like 'the way people deal with conflict determines the consequences'
for a 3 bp piece, I'd break it down to something like the following:
talk about how negative approaches to conflict are bad which they obviously generally are. use examples from text if possible for instance im studying the rugmaker of mazar-e-sharif so i'd talk about the way the taliban deals with people and the suffering it causes, maybe the destruction and loss of life caused by the ongoing afghanistan war
external examples could include wwII or other wars as you have said, but you could maybe talk about riots like the 2005 cronulla riots or something as well
second paragraph you might want to introduce ideas around other ways of dealing with/responding to conflict like the democratic election process, where there is minimal violence even though parties are competing. you should probably look for text based examples to support, and make your external example relate in some way.
third paragraph, maybe talk about good things that have come from conflict that was not dealt with violently. it's a cliche'd example im sure but ghandi's peaceful protests and similar non-violent wars are good to talk about. it might add depth if you bring in the idea that there have in fact been some cases where violence and aggression have resulted in a favourable outcome, i dont know much about it but something like the american civil war that was for freedom and stuff even though it was violent.
im sure there are other ways to write this essay and i dont pretend to have any superiority, i'm only just getting used to context pieces myself, but hopefully these ideas help you write a good piece