Which french city shown on the map changed back from germany to britain?

The question mentioned a map, but then you didn't attach the map so we can see it. I have attached the map to this answer.

The name of the French City that changed back from Germany to Britain during World War I is MAMETZ. This was achieved through the Battle of the Somme where armies of the British Empire and France fought against the German Empire.

Themes; subfields is the answer

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