For Laszlo Petrik, any talk of the Treaty of Trianon stirs up strong feelings. Petrik is an ethnic Hungarian who lives on the Slovak side of the Danube River. His home in Hungary became part of what is now Slovakia because of the Treaty of Trianon, which was signed on June 4, 1920. The agreement led to changes in Europe’s borders after World War I. Some Hungarians look at the treaty as a national trauma because it took away more than 60 percent of the country’s territory. It left millions of ethnic Hungarians living in what is now Austria, Romania, Serbia, Slovakia, and Ukraine.