You can use this lesson as an introductory activity in the beginning of the year. It will lead your students through a discussion of essential questions related to conflict. It's a great way to kick off the school year, get to know what your students know, and prime them to think about these questions all year long.
The presentaiton below will walk you through the three essential questions. Each slide includes a question, some probing questions, and some relevant images. For a "Do Now," you can start with a Think-Pair-Share in which your students talk about a question of their choice.
For more ideas on how best to execute this discussion, read this. The key questions are - why do countries go to war, why should countries go to war, and can countries cooperate.
The lesson ends with a wrap-up writing activity to assess what the students took away from the discussion. You can either have this be an exit ticket or the students can take it home to write it.
While this is a perfectly good activity to do individually, it works best when it's combined with a thematic approach to the curriculum. You can combine these essential questions with others related to the themes of economics, equality, movement of people, and civics. By doing so, you help your students make more connections between different topics and time periods and better understand what they are learning about throughout the year.