A suitcase nuclear weapon, or suitcase nuke, was a term used to describe various types of nuclear devices developed by the former Soviet Union. They, in their various incarnations, were exactly what the name implied: low-yield nuclear bombs concealed inside suitcases. These devices were specifically designed to be mobile and difficult to detect by the hostile military units and intelligence agencies. The terrorist plot in Day 6 involved suitcase nukes: Abu Fayed and Dmitri Gredenko attempted to detonate the bombs on US soil and, later, Cheng Zhi stole an FB subcircuit board to gain access to Russian military technology.