How has war evolved over time? What are the main elements of change and continuity? What factors best explain the changes?

Question 1. How has war evolved over time? What are the main elements of change and continuity? What factors best explain the changes?

Related links for number 1 question:
https://www.youtube.com/watch?v=jlSsSXCIPBs&feature=youtu.be
https://www.youtube.com/watch?v=NYBua8wmKmc

Question 2: How does collective security address the problem of security and conflict, and what are its strengths and weaknesses?

Related links for number 2 question:

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