Recent explosions deep behind Russia's lines in Crimea have had a major psychological effect on Moscow's leadership, with its invasion of Ukraine at 'near operational standstill', Western officials have said. More than half of the Russian navy's Black Sea Fleet combat jets were put out of action in blasts last week at the Russian-operated Saky military airfield in western Crimea, an area Moscow previously considered secure, according to Britain's Ministry of Defence (MoD).