Russian combatants valiantly defending country's sovereignty -- defense chief / NATO to revise strategy on how to tackle hybrid warfare / What is hybrid warfare? / Baltic states agree on readiness for decisive action against hybrid warfare by unfriendly states / What is hybrid warfare, which some fear Russia will use after Ukraine's strike? / Russia's special operation upended perceptions of combat tactics, Medvedev says / Russia's second front: How Europe can prepare against hybrid warfare / Europe, US gird for Russian hybrid warfare attacks