Map of the English channel, ca 1940s
The English Channel was a body of water that linked the Atlantic Ocean and the North Sea together between southern England and northern France on Earth. Dunkirk and Dover both lied along channel.
During the Battle of Britain of World War II, the Jerries had to cross the English Channel to attack England. In a holoprogram enjoyed by Miles O'Brien and Julian Bashir, the two would try to prevent that crossing. (DS9: "Accession", "Looking for par'Mach in All the Wrong Places") The holographic pilot Clive crashed his airplane into the Channel in a session of this program. (DS9: "Homefront")
In another program set in 1944 France, British radio reported low fog across the Channel on September 22nd; the entire weather report contained a secret message to French Resistance fighters in Sainte Claire. (VOY: "The Killing Game")