Moscow's forces have advanced in Ukraine's Zaporizhzhia region, as the U.S. and Russian leaders are expected to speak on Tuesday.

Kyiv's troops are struggling to hold territory in Russia's Kursk region and may be forced to retreat, reports say.

World War I involved 32 nations from 1914 to 1919. It redrew the world map and reshaped many borders in Europe. The collapse of the Russian Empire created Poland, the Baltics, and Finland.