The article is devoted to the study of combat traditions of the Russian Cossacks in the defence of the Motherland, their formation, military development during the Great Patriotic War and reproduction in modern conditions. The Cossacks formed a specific community of warriors who voluntarily took responsibility for protecting the borders and repelling the enemy attacks on their native land. The Cossacks took part in all military campaigns of Russia, legends were composed about their military glory. Cossack formations were distinguished by the status of an irregular army and by the autonomy of military service. They were famous for their combat skills, traditions and the spirit of military brotherhood. Preserving the tragic pages of their history and experiencing today's renaissance, the Cossacks continue to stand guard over national security. The objective of this article is to demonstrate the preserved and currently reproduced military traditions of the Cossack communities. The findings are based on qualitative data obtained during pilot studies conducted by the authors in February-March 2025. The study included an analysis of historical materials and documents, supplemented by in-depth interviews with representatives of the Cossack community, Cossack national squads, and Cossack fighters. The article also provides a historical retrospective of the participation of Cossacks in the defence of the Motherland. Particular attention is paid to participation of Cossack formations in the Great Patriotic War. The status of Cossack communities in the modern national security system, the features of their formation and staffing are being described. The traditional patriotism of the Cossacks is shown, that is characterised not only by a "protective" attitude, but also a "social" one, expressed in labour and altruistic service to their people. Based on the analysis of historical materials and interview data, the authors come to the conclusion that the Cossacks, as a special serving force, continue to preserve and pass on their traditions today. Cossacks respect and honor the military traditions that have developed over a century of their defence and war participation. The Cossack community believes in staunch patriotism, passionarity coupled with altruism, deep Orthodox faith intertwined with ancient superstitious traditions, military art, military camaraderie and regional сommunity.