Have Nuclear weapon made the world safe by functioning as deterrent?

I don't think that the nuclear can be used as deterrent for saving world. The first reason is that each country feel insecure, because other countries try to possess this kind of weapon for self-defense as well. If some countries can originate the nuclear bomb, other countries can have the nuclear bomb too. When they don't trust in each other, they build this weapon as much as they can so as to guarantine their safety. Because they don't know what is going on with the other side's nuclear bomb creation. Nuclear bomb research will be carried on without knowing ending. Conflicts may be arised among these countries which try to produce the nuclear weapon. The more powerful weapon they create the more massive destruction will be followed.
Apart from conflicts probably occur from each nuclear armed countries, there might be a discrepancies between nuclear armed countries and non-nuclear armed countries. Basically the countries can afford nuclear weapon must be the countries are well-econimical status such as United States and United Kingdom. As the production of nuclear weapon costs a lot money. How about developing countries and undeveloping countries? Those poor-econimical status countries can not take possesion of the weapon, the only way for surviving in this curcumstance is choosing one side of nuclear armed countries. A hail of argument amidst these countries are brought up continuously. Where is peace?
The second reason is using nuclear weapon cause loss more than benefit. Considering effect of the second world war II, Japan was the victim of two atomic bombs. More than 100,000 people were killed by dropping atomic bomb. The nuclear bomb have destructive power more than atomic bomb. Can you imagine if one nuclear bomb is dropped in some place in the world, how many people would die because of this? Bringing peace by using the nuclear bomb cause a lot of damage especially dead damage, is it worth using? Not only the loss of death but also the loss of inestimable assest can be occured. Japan is an obvious example of the atomic bomb's victim. Japan spend 20 years on recovering their own country in term of politics, economic and social problems. However, they can solve some problem, incurable problems still stay.
The third reason is that the empowering countries use nuclear weapon as a tool threatening powerless countries. As we know that powerful countries can have nuclear weapon.
These countries take advantage of possessing this weapon to influence other weak countries. Poor-economical status and weak military countries can be the victims of powerful countries.
They involve in term of international politics and economic or other important aspects. Weakened countries lose independent, finally depend on powerful countries. Inequality, Stereotype problem arise synchronizingly.
It is time to consider about using nuclear weapon functioning as deterrent again!! Is it useful or useless?