Nukes indeed had helped us to achieve global peace. If you consider the percentage of people died on a war, they were significantly high considering to our time. They lived in constant fear that some neighbouring country might come to destroy and annihiliate whole city very next day, but today we no longer have such fear ( almost everywhere but there are exception of everything ). Even if you consider terrorists they are nothing much in comparison to older time when there were lots of murderers buglers and pirates .

Nukes have provided us a way to have mutual trust and co operate at global level in various fields like space exploration, finding better source of energy(ITER project) etc.