Thursday is the 80th anniversary of the end of World War II in Europe. As leaders of countries that suffered greatly during and after the war, we attach great importance to this date. We remember our fallen parents, grandparents and other relatives who defended our freedom from two tyrannies of the last century. We remember all those who were killed, including at least six million Jews murdered during the Holocaust by Nazis and their collaborators. We remember the millions of victims of Soviet repressions that continued unabated on the other side of the Iron Curtain at a time when Europe was reuniting and rebuilding itself after the war.

The meaning of commemoration is to draw necessary lessons and to prevent mistakes from happening again. The lessons from World War II — we have five of them to share — are critical for understanding how to restore and maintain long-lasting and just peace and security in Europe today, when they are again at risk.

Just like the great wars in the past, Russia’s full-scale aggression against Ukraine starting on Feb. 24, 2022, divided the 21st century into before and after. Despite overwhelming odds, Ukraine has managed to repel the attack and liberate more than half of the newly occupied territory. But even after more than 950,000 Russian soldiers killed and wounded in action, Russia has not abandoned its aggressive plans.

President Vladimir Putin of Russia hopes to use the current geopolitical moment to his advantage and extract concessions from Ukraine and its partners. Moscow increasingly engages other rogue regimes like Iran and North Korea in the war, threatening the security of not only the European continent but also the Indo-Pacific and the Middle East.

Learning from the past is critical today, as Ukraine, the European Union and the United States work to achieve peace. Russia’s war of aggression has shattered the post-World War II security architecture and the international system based on the United Nations Charter and the Helsinki Accords. Its conclusion will form the foundation for a new architecture. We offer the lessons from World War II that must be taken into account if we want to create an enduring peace in Ukraine, rather than a pause before the next potentially disastrous global conflict.

Appeasing the aggressor leads to more aggression, not peace. Concessions on unlawful territorial claims are a disastrous mistake. The partition of Czechoslovakia in 1938 only fueled Nazi Germany’s appetite and resulted in a global war. Learning from this lesson, Ukraine will never accept the legitimization of Russia’s occupation and annexation of any part of Ukraine’s territory. Respect for territorial integrity is a fundamental principle of international law. There will be no sustainable peace and security at the cost of Ukraine’s people, independence, sovereignty or territorial integrity.