The primary reason for war
Is it the individual, or is it a group?
Perhaps it’s the State , and/or its decision makers?
Is it ideology?
Maybe it’s to be found in social and economic factors?
Or something else?
Once you have decided on your primary focus, you should explore how other factors, as expressed in the questions above, may contribute to the primary focus.

some resources that could help, are two movies 1.The Fog of War and 2. The Most Dangerous Man both deal with Vietnam era and the book identity. At least 7 sources