The British start defence preparations in readiness for the "Battle of Britain"
During the time between Dunkirk and the "Battle of Britain" the British Government prepared a multi-level strategy to deal with the problem, lookouts were positioned to report enemy activity at all potentially suitable landing sites, also obstacles were placed on the threatened beaches including anti-tank and anti-landing craft devices, some beaches were heavily mined and the ringing of church bells was banded to allow their emergency use as an invasion warning, this was a fallback system in case conventional communications were disrupted by German Forces, additionally road signs were removed to make navigation harder for an invasion force and the LDV "Local Defence Volunteers" (a.k.a. "Home Guard" or "Dads Army" -) was formed using those to old to be conscripted or in reserved occupations. The manufacturing of the RAF's latest modern monoplane fighters, the Spitfire and Hurricane, was given the highest priority utilising the UK's car industry as it's industrial manufacturing base. The British top secret Radio Detection and Ranging network (RADAR) called "Chain Home" and "Chain Home Low" was expanded and calibrated as much as possible, the phone lines which connected the radar operators to their operation rooms were buried deep underground and protected with concrete against bombing (Radio links could be easily jammed of monitored). Prior to The Battle of Britain the ROC (Royal Observer Corps) established over 1000 observation posts to report enemy aircraft formations altitude, direction, aircraft type and magnitude. These ROC reports proved invaluable as the primitive "Chain Home" radar network used in the Battle of Britain was limited in resolution and was potentially it's self a major target for the German Luftwaffe bombers during the "Battle of Britain".
Civil defence measures implemented prior to the start of the "Battle of Britain"
To protect the British civilian population from possible terror bombing by the German Air-Force (Luftwaffe) during the Battle of Britain, children were evacuated from Cities and other areas considered at high risk into safer areas, often into the countryside, pre-fabricated corrugated iron air-raid shelters called "Anderson shelters" were issued on request by city councils to city houses, gas masks were issued to everyone (even babies!). Black out procedures were initiated at night to make cities less obvious to Luftwaffe bombers and aid raid wardens empowered to enforce them. Volunteer "Fire Watchers" were tasked to look for fires from observation posts on the top of high buildings during air-raids and report their observations to the fire and rescue services by phone.
Winston Churchill makes contingency plans in case the "Battle of Britain" is lost
Fall back strategies were also formulated should the "Battle of Britain" be lost and the German invasion be successful, these consisted of moving the Royal Family and Government to the colonies to continue the fight from the colonies with the protection of the Royal Navy who would still be effectively "ruling the waves", additionally supplies of weapons, ammunition and explosives were cashed secretly, their locations made known only to a chosen few, these were people not intended to fight directly against an invasion force, but fight a gorilla war of attrition against the German forces after they had actually completed their occupation of Great Britain.
Germany plans operation Sea Lion - The invasion of Great Britain by sea
We can look back now and see that the logistics of a successful landing by the German forces were highly unlikely - the logistics needed for operation overlord were in fact far beyond the Germans ability at this time, however, this did not seem to be so at the time by either side, the German Blitzkrieg methods which had so rapidly overrun Europe were strongly based on the unprecedented rapid, and to a degree, unexpected attack by panzer divisions supported by the Luftwaffe. The German forces had the most modern aircraft and tanks in the world, and as a result of their involvement in the Spanish civil war, their armed forces were battle experienced and had been honed to a high level of readiness. The unbelievable speed the had conquered mainland Europe and all it's armed forces had given most the impression that they were unstoppable and invincible, consequently many Britons and Germans thought that Great Britain would loose the "Battle of Britain" !
The English Channel and the strength of the Royal Navy results in the Battle of Britain becoming an air war
Unfortunately for the Germans the English Channel, although narrow, presented an almost impossible barrier, the German Navy could not remotely hope to land a sufficiently large invasion force with their existing ships against any serious opposition from naval or airborne forces. The Germans excellent submarine U-boat force was of little use in the shallow and relatively narrow English Channel and the German navy lacked the numerous landing vessels required. The German response to these obvious problems was to scour occupied Europe for barges and convert them into landing ships, some had their bows hinged so they could carry tanks and other vehicles, many of the barges were un-powered and would have to be towed coast to coast, the plan required very calm waters and therefore had a limited window of opportunity as the winter weather would make the plan impossible. Once the German forces were gathered and sufficient barges were available Herman Goring was ordered by Adolf Hitler to destroy the RAF in the "Battle of Britain" in order to make the dangerous trip across the English Channel possible for an invasion force and to do so before the winter weather made operation "Sea Lion" impossible.
The "Battle of Britain" begins as Field Marshal Herman Goring executes operation "Eagle Day"
The "Battle of Britain" had two distinct phases, initially in the "Battle of Britain" an attempt was made to destroy the RAF and it's support info-structure, this was initiated by the execution of operation Eagle Day and marks the beginning of the Battle of Britain. Operation "Eagle Day" was meant to cripple the RAF in days giving the Luftwaffe air superiority over Great Britain, and totally destroying the RAF within two months. The reality of the opening period of the Battle of Britain for the Luftwaffe was not as expected, the RAF was still effectively intercepting German bomber formations and for the first time ever the Luftwaffe was suffering unacceptably heavy losses, they were in fact considerably worse than the RAF's. The massive air-battle that followed had no precedent and was later to become known as "The Battle of Britain" and the RAF pilots who fought in the battle known as the "The few" following Speeches made by the British Prime Minister Winston Churchill. The inability of the Luftwaffe to win a quick decisive German victory in the "Battle of Britain" presented new problems which had not been evident before, experienced RAF fighter pilots and aircrew who successfully bailed out of their aircraft during the "Battle of Britain" could be flying again the same day in new aircraft, their close escape often leaving them better prepared for the next "Battle of Britain" engagement. A German pilot, or his aircrew, bailing out over Great Britain during the "Battle of Britain" was destined to spend the rest of "Battle of Britain" and in fact the rest of WW2 as a prisoner of war, new replacement pilots and air-crew normally had less experience than their predecessors and were even more likely to be shot down themselves in the "Battle of Britain" air war.
Luftwaffe losses result in the "Battle of Britain" having "Blitz" terror bombing added
As German losses increased in the "Battle of Britain" , and air crew losses got worse, a switch in targets and tactics was initiated. RAF targets were replaced by civilian ones and the terror bombing of cities began, there was also a switch from daylight bombing to night bombing in an attempt to reduce Luftwaffe losses. It was thought by the Germans that the terrified populace would force the Government of Great Britain to surrender, this proved to be a big mistake, the terror bombing merely strengthened the British resolve never to surrender, the British people soon began calling these new terror air raids at night the "Blitz". The reduced pressure on the RAF's airfields and aircraft factories gave the RAF time to make good it's own losses from the first phase of the "Battle of Britain and prepare to take the offensive for the first time.
The "Battle of Britain" is won and the 1940 German invasion plan is cancelled
As the winter approached Adolf Hitler had to delay operation Sea Lion until the next year following the Luftwaffe's failure in the "Battle of Britain", however, by 1941 Great Britain was clearly on an offensive footing and invasion of the British isles was clearly less practical than it had been in 1940. Once Russia And the USA entered WW2 the chances of a successful German invasion of Britain had changed from difficult to unlikely to imposable. The "Battle of Britain" proved to be the turning point for Nazi Germany, the rapid and decisive Blitzkrieg attacks being replaced by a gradual but continuous retreat and the eventual total surrender to Allied forces.