What is classis britannica?

Classis Britannica

The Classis Britannica (literally, British fleet, in the sense of 'the fleet in British waters' or 'the fleet of the province of Britannia', rather than 'the fleet of the state of Britain') was a provincial naval fleet of the navy of ancient Rome. Its purpose was to control the English Channel and the waters around the Roman province of Britannia. Unlike modern (and some contemporary Roman) "fighting navies", its job was largely the logistical movement of personnel and support, and keeping open communication routes across the Channel.

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Some articles on classis britannica:

Classis Britannica - Ports and Harbours
... forts occupied by the fleet's marines at Dover, suggesting this was in fact a major base of the Classis ...