The “de-coupling” US Under Secretary DiNanno refers to is a technique for disguising a low-yield nuclear blast by conducting the detonations in a large underground cavern to disperse its seismic effects. As arms control expert Jeffrey Lewis of the Middlebury Institute of International Studies at Monterey describes: “…decoupling is when one explodes a nuclear device inside a cavity, usually one created by a prior nuclear explosion. This makes the yield look 20-40 times smaller than it really is (assuming rock at a place like Lop Nor).”