The size of the world's nuclear arsenal has quietly increased in several countries amid fears of World War III. Five countries - China, Pakistan, India, Israel, and North Korea - have increased their nuclear stockpiles by over 700 warheads over the past 40 years. The US government announced last month that it will also restart its nuclear testing programs in secret underground facilities. According to the data from the Federation of American Scientists, there is clear evidence that five nations have seen their nuclear stockpiles grow since 1986. The think tank said that the US was still the most transparent nation when it comes to the size of their nuclear arsenal, noting that the country's allies in Israel were the most secretive.