The text says that the two major problems to nuclear disarmament are vertical proliferation and horizontal proliferation. Using support from the text, what does it mean when something proliferates? What makes these two forms of proliferation so deadly?
When something proliferates, it grows in numbers. If the number of countries with nuclear weapons is growing, and the number of nuclear weapons is increasing within countries that have already possessed them, it becomes increasingly difficult to track the number of nuclear-capable countries, as well as the strength of each. It also increases the number of countries you need to agree to cease nuclear development and get rid of nuclear arsenals.