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German Submarine Zone, February 1915
Map showing submarine warfare zone around the United Kingdom, declared by Germany on February 18, 1915.
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Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:
"German Submarine Zone, February 1915."
http://en.wikipedia.org/wiki/File:German_Submarine_Zone_February_1915_after_Reynolds_et_al.jpg
Wikipedia
Public domain.