Computers cannot prevent wars. Scientists are working on how they can help prevent earthquakes, tsunamis and other natural diasters. They can definitely be used for good and bad. To increase the quality of life or to destroy lives by constructing dangerous machines. But, they cannot prevent wars

Perhaps you wanted to ask if computers can prevent an apocalypse from happening.

https://venturebeat.com/2017/10/29/4-ways-ai-will-prevent-not-cause-an-apocalypse/

Unfortinitly you cannot prevent wars with computers because wars are cause due to on offensive attack or if the side wants to conquor more land then wars can break out.