https://en.wikipedia.org/wiki/East_Karelia
East Karelia (Finnish: Itä-Karjala, Karelian: Idä-Karjala), also rendered as Eastern Karelia or Russian Karelia, is a name for the part of Karelia that since the Treaty of Stolbova in 1617 has remained Eastern Orthodox under Russian supremacy. It is separate from the western part of Karelia, called Finnish Karelia or historically Swedish Karelia (before 1808).