How Poland Drifted to the West

Today's #30DayMapChallenge is Polygons . At the risk of starting World War III, I've created a map of Poland's Historical Borders . The map uses polygons to show how Poland's borders have changed at different points in its history. The historical boundaries were downloaded from OpenHistoricalMap . The map includes three snapshots: the semi-autonomous Congress Kingdom of Poland in 1815, the Second Polish Republic immediately before the German and Soviet invasions of 1939, and the post-war borders established in 1945. But rather than simply displaying these three historical boundaries, I thought

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