Nuclear deterrence is set to be a hot topic at the Munich Security Conference, which starts on Friday. Europe depends on the US for its so-called nuclear umbrella, comprised of American weapons based on the continent and NATO’s mutual defense pact. If the US can no longer be trusted, Europe is faced with the sinister prospect of being home alone with a neighbor, Russia, that owns the world’s largest nuclear arsenal. Bloomberg's Andrea Palasciano reports. -------- More on Bloomberg Television