The fourth Nuclear Security Summit, to be held in Washington on Thursday and Friday, is one of the few major signature programs initiated by US President Barack Obama. The others include health reform, financial reform, ending the war on terror, resetting US-Russia relations, Global Zero and mitigating climate change etc.

Obama has succeeded in his climate change agenda, but failed in "resetting" relations with Russia. The withdrawal of US combat troops from Iraq seems to have caused more harm than good, given the rise of the Islamic State, and he has not made any substantial progress on the Global Zero campaign to eliminate nuclear weapons. In the light of these facts, the Nuclear Security Summit has become Obama's major policy initiative to promote global security against nuclear terrorism.

Nuclear security is a very important security issue. Given the lethality of nuclear weapons, the wide use of civilian nuclear energy and the transnational nature of global terrorism, and the possible coupling of such elements, the international community is haunted by the nightmare of nuclear terrorism. Fears over the theft of nuclear weapons and materials, as well as sabotage of nuclear facilities, are well founded. Indeed no nuclear-capable state has impregnable nuclear security, as assessed by the three Nuclear Materials Security Indices, published by the Nuclear Threat Initiative in 2012, 2014 and 2016.