What are some ideas for a speech on conflict about war?

Because this topic is so broad, there are infinite directions that you can take it!
One interesting topic would be justifications of war. This could be a discussion of what constitutes a just war; you could juxtapose that with what makes a war unjust. You could include examples by finding a war that you think was justified (example: World War II) and then explain why it was justified (example: because it ended a genocide). Then compare it to a war that you think is unjustified and discuss what the characteristics are that make a war justifiable or not.
Another interesting topic would be comparing two wars that happened around the same time such as the American Revolution and the French Revolution. You could investigate the ways that the revolutionaries in France developed their ideologies considering the ideologies of the American revolutionaries. The same would work for many different couplings of wars.
Similarly, it might be interesting to discuss the stages of a revolution (normal, criticism of the current regime, widespread dissatisfaction, transfer of power, civil war, reign of terror, and recovery). You could analyze these stages using any revolutionary war. 
One more interesting topic would be the concept of foreign involvement in wars: how third party nations become involved in wars and their role. You could discuss this based on a certain war such as the Korean War or in terms of one nation that becomes involved in conflicts such as Great Britain.
Any one of these would be a very compelling speech.