After World War II, people continued to develop new weapons, including intercontinental ballistic missiles. People became concerned about weapons of mass destruction, weapons that can kill many people very fast, and are usually cheap and easy to make and use. One kind of weapon of mass destruction is poison gas. New kinds of poison gas, such as nerve gas, are much more powerful than the old kinds. Another kind of weapon of mass destruction is disease germs, which could be used to make many people sick and maybe kill them. 