Vladimir Putin lowered the threshold for Russia's use of its nuclear weapons after signing a revamped policy- but what is in the chilling document? The 4-year-old document is called “Basic Principles of State Policy on Nuclear Deterrence” - but its contents are alarming , especially with Putin's newest revisions. The Russian leader first announced changes in the nuclear doctrine in September, when he chaired a meeting discussing the proposed revisions. He has previously warned the U.S. and