The successful development of Focus Fusion could improve the chances for world peace in several ways. First, since energy produced from Focus Fusion would be cheaper than oil or gas, it would start reducing the demand for these resources, and quite rapidly cause the price to fall. As oil and gas become less valuable, and less essential, wars over oil and gas will become a thing of the past.
Second, Focus Fusion would end all threat of nuclear proliferation. Focus Fusion could make uranium enrichment obsolete because, if it works, aneutronic-fusion-produced electricity would be cheaper than any available today.
Aneutronic fuels produce energy that can be converted directly into electricity, without going through the expensive cycle of generating steam and putting it through turbines. Such an ideal energy source would be far cheaper than nuclear fission energy based on uranium (what is commonly called nuclear energy). There would be no reason for any country to continue to pursue fission energy for peaceful purposes. To prevent nuclear weapon proliferation, the use of uranium could be universally banned as nuclear fission energy production was shut down. We could put lock on uranium mines (their locations are well-known), shut down existing fission reactors as Focus Fusion came on line and eliminate all possibility of the production of new nuclear weapons. Hopefully we could then get rid of existing ones as well.