The major obstacle to nuclear terrorism is not obtaining the weapon. It is obtaining the terrorist group. A single terrorist fired the weapon that ignited World War 1. When the Archduke Ferdinand died, Europe erupted into a war, which resulted in the deaths of millions. Not since then has a single individual or small group been able to commit an act that has caused such devastation. Until a few years ago, the repeat of such an act would seem unlikely.
Today, a terrorist act resulting in millions of deaths is increasingly likely. A single nuclear weapon in the hands of a well-funded, technically able, and properly motivated individual could result in upwards of millions of deaths. The act that started World War I, the assassination of the Archduke was committed by the Black Hand, which was sponsored by Serbia. The gunman, Gavrilo Princip, was captured. Serbia was destroyed in retribution. While the assassination was successful, the consequences greatly outweighed the benefits. Traditional terrorist organizations have had one or more limitations, which prevented them from committing acts or large-scale terror: retribution or loss of support. Retribution is the limiting factor for state-sponsored and economic-based terrorist groups. State sponsored terrorist groups have to temper their attacks, unless their parent-state faces the retribution as in the example of the Black Hand and Serbia. Irani-sponsored Hezbollah appears to be in an all out war with Israel. However, they are conducting a series of attacks designed to turn opinion in the Arab-Persian world against the Israeli