The reasons war break out is usually due to countries having claims on the same land. So, I think there should be cores of a nation on other countries' land.
For example,
For example,
- Germany having cores on Strasbourg/Strassburg as well as France, as Germany once owned Alsace-Lorraine
- Germany having cores on Danzig and Bydgoszcz, as Germany once owned the land.
- Nationalist China and Communist China having cores on all Chinese lands, including Sinkiang, Tibet, and Manchukuo, in the 25 player world
- Northern States of America and Southern United States having cores on each other
- Mexico having cores on Texas, California, and Arizona
- Austria and Hungary having cores on all lands previously owned by Austria-Hungary
- Soviet Union and Russian Empire having cores on each other, Ukraine, eastern Poland, and the Baltic States
- Bulgaria having cores on Kavala, Greece
- Greece having cores on Nicosia/Cyprus, and Rhodes Island in historical maps
- Poland and Lithuania having cores on west Russia and East Prussia/Konigsberg, on the land formerly owned by the Polish-Lithuanian Commonwealth
- Sweden having cores on FInland, the former vassal of it as the Swedish Empire
- Yugoslavia and Italy share cores on Trieste
- Ukraine and the Russias having cores in the Crimean Peninsula