The British Expeditionary Force (BEF) was lifted off the beaches at Dunkirk by the Royal and Merchant Navies. Unfortunately, almost all the British army's equipment was left behind. It was considered fortunate if soldiers managed to bring their personal weapons off with them; many did not.
On 3 July 1940 the Royal Navy opened fire on French warships berthed at Oran. With no British losses, it was a one-sided battle that ended with the destruction and immobilisation of the French force.
Britain now faced a serious strategic dilemma. Germany controlled the Atlantic seaboard (from the North Cape of Norway to the Spanish frontier) and by July 1940 the Germans were already basing their U-boats in the French Biscay ports. The ports provided the Germans with a point of safety for surface raiders and blockade-runners. With aid from alliances in Eastern Europe and resources taken from overrun Poland and Western Europe, Germany secured massive economic resources for its war effort.
In the Battle of Britain, Germany attempted to win air supremacy over southern Britain as a precursor to invasion. There were heavy losses on both sides, but thanks to RAF air defences and German fears about the Royal Navy, the threat of immediate invasion passed. The Germans then began bombing British cities by night, and although the RAF was successful in deflecting a German aerial blow in daylight, the switch to night attacks posed technological problems that took time to solve. Only strategic bombing by the RAF now held out any hope of weakening Germany.
German attacks on cities tailed off during early summer 1941 and there was a lull until spring 1942. The Baedeker raids from April until the end of July 1942 were reprisal attacks for Bomber Command offensives against Germany. Many provincial cities were targeted and some, such as Exeter, suffered exceptionally heavy damage.
On 8 September 1944 the first V2 rocket fell on Britain, landing in Chiswick. By the 18 September, 27 V2s had fallen, 16 of them on London. The offensive into Holland brought the attacks to a temporary halt but the next series attack came in 1944 with the deployment of German V1 and V2 missile systems. On 20 June 1944 the Cabinet Committee 'Crossbow' was set up to consider counter measures. By September 1944 allied ground forces had overrun the German launch sites, and the V1 attacks petered out. From October 1944 to March 1945 V2s fell regularly on the UK; only the advance of the Allied armies and the destruction of the German transport network brought the offensive to a halt. The air attack on Britain was over.
Before Dunkirk, measures had been taken to improve home defence - the most famous being the formation of the Home Guard. After Dunkirk, with the army in a woeful state and with the Battle of Britain under way, risk of invasion seemed high. The Royal Navy kept cruisers and destroyers close to the straits of Dover as well as having the Home Fleet on stand-by in case of a seaborne invasion. The longer the Germans waited, the better equipped the land forces became. The Royal Navy's ability to close the channel at night now posed an almost insoluble problem for the German Navy.
Invasion fears reached a climax on 7 September 1940. An attack seemed imminent between 8 and 10 September. The 'Cromwell' code was issued, signalling maximum readiness to the land forces (the Navy and Air Force were already prepared), but unable to secure local air superiority, the Germans scaled back their plans. British invasion fears finally disappeared when Russia was invaded by Germany.