sentences:  Highly-accurate strategic missiles like the Trident II can also be used in substrategic, tactical strikes.According to several reports, including by the Carnegie Endowment for International Peace and Bulletin of the Atomic Scientists, as a result of the effectiveness and acceptability of USAF use of precision munitions with little collateral damage in the Kosovo conflict in what amounted to strategic destruction once only possible with nuclear weapons or massive bombing, Vladimir Putin, then-secretary of Security Council of Russia, formulated a concept ("“escalate to de-escalate”") of using both tactical and strategic nuclear threats and strikes to de-escalate or cause an enemy to disengage from a conventional conflict threatening what Russia considers a strategic interest.The lowered threshold for use of nuclear weapons by Russia is disputed by other experts.