Now that you mention it - of course.
“Most disturbing, Moscow’s nuclear saber-rattling raises questions about Russian leaders’ commitment to strategic stability, their respect for norms against the use of nuclear weapons, and whether they respect the profound caution nuclear-age leaders showed with regard to the brandishing of nuclear weapons,” - SecDef Ash Carter, today
http://hosted.ap.org/dynamic/stories/U/US_CARTER_DEFENSE