National Unity Day is observed in Hungary every June 4. This official remembrance day has been commemorated since 2010 and marks the anniversary of the signing of the Treaty of Trianon, which concluded World War I between the Allies and the Kingdom of Hungary. The treaty resulted in Hungary losing 72% of its territory and 64% of its population, leaving only about 30% of Hungarians within the new borders. The ten largest cities of the kingdom were ceded to neighboring countries, and the treaty imposed significant military restrictions on Hungary. The signing is viewed as a national tragedy, leading to a period of mourning that lasted until 1938. National Unity Day serves to remember these historical events and their impact on the Hungarian nation.