I agree with your answer. The Buddha successfully took a similar approach 2,500 years ago. He spoke to the soldiers, officers, generals, and kings lined up for battle on two sides of an imminent war. The war was triggered by a famine. Each side (or maybe just one side) wanted more land so they could grow more food. The Buddha listened to their reasons, and then pointed out that the war might give them more land, but would kill people and take time from tilling the fields, so that the benefit of more food and more life would not be realized.
When we can show that war does not even accomplish the goals intended for it, that helps prevent war.
For example, the United States is engaged in a war on terrorism, but is killing tens of thousands of innocent civilians in the process. Certainly, their families are more likely to be anti-US terrorists in the future, having family members killed by Americans. When we can see that war doesn't work, we will stop making war.