The capitulation of the Netherlands, Belgium, France, Denmark and Norway in mid-1940 left the United Kingdom facing hostile coastlines from Norway to the Bay of Biscay. In the west, the Battle of the Atlantic was taking place. Winston Churchill rejected Adolf Hitler's overtures for a peace settlement and the Nazi leadership resolved to invade Britain as a last resort. Operation Sea Lion could not begin until air superiority over the Channel and Southern England was achieved, at the least. ordered attacks on British shipping in the English Channel as a prelude to a full-scale offensive against Fighter Command and its infrastructure, in July 1940. The intention was to draw out Fighter Commandand deplete it in dogfights over the Channel while blocking the Channel to British shipping. The Germans referred to this phase, of what became the Battle of Britain, as the .