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MARGIT LEERIMAA
Secretary-General
Estonian Atlantic Treaty Association
Since 1 September 2025, the association has been led by Margit Leerimaa, who began working as a national defence education teacher in 2012 with the aim of encouraging young people to take an interest in national defence and contribute to it. Currently, Margit is a national defence education teacher at Kaarli School and Tallinn Pae Gymnasium.
Thanks to national defence education classes and other conferences and events on security and safety, she became acquainted with Krista Mulenok and the activities of the Estonian Atlantic Treaty Association, and wished to contribute more than merely as a listener. Margit has been a member of the Estonian Atlantic Treaty Association since March 2023. In the Parempoolsed party, she is Vice Chair of the Foreign and Security Committee. In 2024, she began studying political science at Tallinn University with the aim of broadening her horizons and pursuing personal development. Her interests include national defence, reading, and sports.
KARL MATTIAS SEPP
Team Europe member, European Commission guest lecturer
President of YATA Estonia
Deputy Secretary-General of EATA
Karl Mattias Sepp (29) is a project manager and conference organiser whose work focuses on European and transatlantic security issues and on involving young people in substantive policy discussions. He is a Team Europe member, European Commission guest lecturer and President of YATA Estonia and Deputy Secretary-General of the Estonian Atlantic Treaty Association (EATA).
Karl has worked as a project manager at the British-Estonian Chamber of Commerce and organised the NATO–EU Roundtable conference in 2020–2025. In addition, he has led various Baltic youth conferences and conducted NATO North Atlantic Council (NAC) simulations for university and upper secondary school students, bringing together future opinion leaders, experts and decision-makers, and making complex international processes practically understandable.
“In fact, I also ended up at the Estonian Atlantic Treaty Association through a rather unique role — as a job shadow. Namely, I was supposed to come and get acquainted with EATA’s work for one day. That day, I met colleagues and at one point I noticed that while talking about NATO, the association, the past and the present, six hours had passed unnoticed. During the nonstop discussion I also floated a couple of ideas on what could be done for NATO’s 70th anniversary in 2019. The next day I was already invited to meet the organising team and then, as they say, ‘the rest was history’.”
HANNA-STIINA TORNIUS
Member and Project Manager, Estonian Atlantic Treaty Association
President of YATA Estonia (2024–2026)
International Coordinator of YATA Estonia (since 2026)
Hanna-Stiina Tornius has contributed to the activities of the Estonian Atlantic Treaty Association since 2022. Hanna-Stiina began as an intern, but also became a member of the association in 2023 and has since led two projects: the “Building Resilience with Estonian Youth” school visit campaign in 2023 and the “School Media 2.0: Information Communities and Influencers in the Post-Truth Era” conference in 2024. In 2024–2026, Hanna-Stiina served as President of YATA Estonia and has actively contributed to organising EATA’s annual conferences and increasing the association’s visibility at various events.
Hanna-Stiina has completed a degree in political science at Tallinn University and continues her master’s studies in international relations at the University of St. Gallen in Switzerland. Her main area of interest within both curricula is international security, which also brought Hanna-Stiina to the Estonian Atlantic Treaty Association. In addition, she has volunteered with several youth organisations and was selected in 2023 to serve as Estonia’s UN Youth Delegate with a one-year mandate. Since 2026, Hanna-Stiina has been the International Coordinator of YATA Estonia.
MARICA LILLEMETS
Media Consultant
Marica Lillemets is a journalist by profession, holds a master’s degree, and graduated from the University of Tartu in 1983, after which she worked as a business journalist, editor and/or programme host at Aja Puls, Eesti Ekspress, TV3 and ETV for a total of nearly 22 years.
Later, Marica furthered her education in international economics, banking, business journalism and organisational management in Tallinn, London and Dublin. In addition to Estonia, she has worked in the USA, Russia and elsewhere, in a total of six different countries.
As a media adviser, Marica has been cooperating with the Estonian Atlantic Treaty Association for over 15 years, managing the association’s relations with the press.
KERSTI SIILIVASK
Project Manager
Kersti Siilivask has been a member and project manager of the Estonian Atlantic Treaty Association since 2015 and served as President of YATA Estonia in 2015–2021.
As a project manager, she has successfully carried out the conference dedicated to Holocaust remembrance “Is It Possible to Learn from History?”, the Baltic–Russian Youth Forum in Lithuania, and for 9 years the “Women, Peace and Security” conferences. The international conference discusses the importance of involving women in ensuring security processes both globally and from a local perspective.
Kersti has completed a master’s degree programme in international relations at Tallinn University.
MARIITA MATTIISEN
Volunteer
DMITRI DRJUKOV
Volunteer
HEIDI TORMET
Volunteer