GAS-photo/Shutterstock The global nonproliferation system underpinned by the nuclear Non-Proliferation Treaty (NPT) faces two enormous challenges: vertical proliferation from states with weapons building who are modernizing their arsenals and horizontal proliferation from countries aspiring to acquire them.Horizontal proliferation could be driven by concerns that Washington鈥檚 long-standing nuclear 鈥渦mbrella鈥� over allies in Europe and East Asia is retracting. But the nearest-term threat comes from Tehran whose threshold nuclear program puts it on the precipice of NPT withdrawal.Other states with civil nuclear programs, including Japan, the Netherlands and South Korea, could theoretically be spurred to pursue a weapons program in previously unimaginable scenarios such as a US withdrawal from Nato or a Chinese invasion of Taiwan. Save for later Print Download Share The Issue
