The article explores Ukraine’s journey toward the development of its national cybersecurity system, building cyber resilience and cyber defence capabilities in countering Russian cyber aggression, and the lessons learned that may be valuable for other European nations. It analyses Russia’s tactics in cyber warfare and their gradual transformation, and examines the growing Russian cyber threat to EU countries. This Tallinn Paper aims to propose ways to strengthen Europe’s collective cyber defence based on Ukraine’s experience. The study is based on scientific articles, analytical materials and statistical data from open sources, as well as open public information created and used by the main entities of the national cybersecurity system of Ukraine when ensuring cybersecurity. It delivers twelve key and context-specific recommendations on building effective national cyber defence capabilities and proposes the creation of a Cyber Alliance to prevent and counter Russian cyber threats.