… crossing only the borders as they stood in
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Name the countries you would cross on land to get from the first country to the second, as the borders stood in that year. Each guess is coloured by how close it is to a shortest route. You win as soon as your guesses join the two countries. When a route ends, the next one, on a random year's map, loads by itself.
Modern names work too: "Turkey" finds the Ottoman Empire in 1910. Islands and sea crossings don't count.