Russian threshold for using tactical nuclear weapons is lower than Moscow has ever publicly admitted, according to leaked Russian military files. The files also revealed that Russian forces have rehearsed using nukes at an early stage of conflict with a major world power, the Financial Times reported. The documents, shown to the Financial Times by Western sources, consist of 29 secret Russian military files drawn up between 2008 and 2014. The documents include scenarios for wargaming and presentations for naval officers, which discuss operating principles for the use of nuclear weapons. Watch the video to find out more.