Operation Sea Lion
Operation Sea Lion (German: Unternehmen Seelöwe) was the codename for the German invasion of the United Kingdom.
History
Background
With the near total destruction of the British Expeditionary Force at Dunkirk, save a few lucky stragglers, the United Kingdom had lost most of it's army from the very get-go of the war. Despite the Commonwealth and the Empire at it's side, the British of 1940 found themselves at a distinct disadvantage, both in terms of material and manpower. Its calls for aid from the United States fell on deaf ears, with president Kennedy continuing his policy of isolation, much to the detriment and dismay of Prime Minister Winston Churchill, who still persisted in vain that 'The new World would come to the rescue of the old'. This deficit of both material and political support from overseas was only further compounded by the lack of good fortune afforded the Allied war effort in North and East Africa, both failing to achieve any significant victories, further increasing casualties and isolating Britain from her Empire, a state of affairs which couldn't afford to persist, lest the home isles lose the ability to maintain her vast Empire. Worse still, the loss of Gibraltar cut the Royal Navies range and available ships in half, with many of the more significant assets having been allocated to support the war in Africa and try to maintain the tenuous hold that the British had on it's supply of oil from the Gulf.
When America finally committed to the War, it was only under her own terms and even then following her power being significantly stifled, following the attack upon the US installations at Pearl Harbour by the Empire of Japan and the subsequent declaration of war by Germany, American aid came too little too late to save the British efforts in Africa and to assist the now collapsing Union of Soviet Socialist Republics, trampled by the German war machine, whilst the Italian East African campaign and North African campaigns were drawing down in earnest, following multiple defeats and a rapidly disintegrating British army. Worse still, said attack on the United States also heralded the Japanese war upon Britain's own holdings in East Asia, costing the British only further lives and material, even threatening the already tenuous grasp upon India that Britain still held. This was not to last, as in the very same that the Empire truly hit it's lowest point, 1943 saw the end of the British Raj and the resources it afforded said Empire, signalling not the nadir of the Empire, but it's demise.
By 1943, the British Empire had all but ceased to exist, as a matter of practicality, surviving only in name and by territories in the Caribbean and in the Dominions and Commonwealth, though even this certainty wavered, notably in Oceania. Yet still, in the face of growing uncertainty and adversity, the British nation fought on. The home front remained as resilient as it had ever done, whilst the channel presented the still intact image of an unassailable island nation, free from the threat of invasions that had all but swept away the less fortunate Continental nations of Europe. However, as all the fortunes of a Free Europe had, this brief period of hopeful optimism, or blissful ignorance, was to be dashed in the very same year of the Empire's collapse.
The German Reich had since 1940, in anticipation that Britain would react stoically to the travails of war as they had done the loss of the British Expeditionary Force and the Fall of France in 1940, began preliminary preparations to launch an invasion of the British Isles, to knock the British Empire from the war and thus end the war in Europe in favour of the Reich. The Battle of Britain, which had seen the Royal Air Force severely damage the Luftwaffe, had taught the Germans the value of caution, German Fuhrer Adolf Hitler showing unusual and uncharacteristic restraint, seemingly unwilling to commit the Luftwaffe to the slaughter they had experienced in the skies, instead opting to bleed the Royal Air Force slowly whilst building up his own airpower. Through targeted Strategic bombing on British industry, aided by the unwitting ally of President Dewey and his reluctance to supplement the British with any aircraft from American reserves, the Royal Air Force began to suffer in operational range and arsenal, with the coveted and much feared Spitfire appearing less and less frequently outside of Home Isles bombing group interceptions.
Despite hesitancy from both the Kriegsmarine and even Adolf Hitler himself, the war would be so favourable to the Germans, from Africa to East Asia and even to Eastern Europe, that soon any doubts whatsoever of the success of a combined arms invasion of the British isles quickly vanished, replaced with the ever present Prussian self-confidence and National Socialist rhetoric. Particularly to the Germans favour, was the willing ally in Éamon de Valera that the German Foreign Office had found, with promises both realistic and somewhat fantastical to the Republic of Ireland, in exchange for cutting the British Isles in half and severing the link to the North Atlantic that would otherwise remain unmolested by any German invasion from mainland Europe.
In the years since 1940, the German war machine had been allowed both the time, resources and the manpower necessary to prepare the perilous voyage across the Channel, with the Wehrmacht and Luftwaffe being supremely confident of the coming operation, whilst the ever sceptical ranks of the Kriegsmarine still doubted it's odds in a one-to-one fight with the still feared Royal Navy, though these concerns were promptly overruled. Now, with Irish compliancy and the logistics to ensure a nominal chance of success for any landing thus assured, the German High Command ploughed ahead with the final, meticulous preparations for the Operation, with the details of each landing zone checked and then double checked and strategic targets assessed and then re-assessed, the last vestigial doubts of a defeated German army of 1918 had evaporated, giving way to a revanchist Germany, poised to strike the final blow.
Invasion
In July of 1943, the long awaited invasion commenced, landing in the English Counties of Kent, West Sussex, East Sussex, Isle of Wight, with the Royal Navies remaining assets that weren't trapped in either the Mediterranean or hopelessly stranded in the Pacific, powerless to affect the outcome of the Kriegsmarines landings coupled with the Invasion of Northern Ireland launched by the Irish themselves to assist the Germans. Whilst the invaders were desperate to keep the bridgehead and landing zones as wide and unassailable as was possible, the defenders were scrambling to respond to the more immediate threat of the existing bridgeheads, attempting to forestall further landings and scrambling the Royal Air Force as best as could be managed, all whilst the immediate evacuation of senior government officials and the Royal Family itself was enacted, despite significant reluctance from both King George VI and Prime Minister Winston Churchill to abscond from the capital in the dire circumstances. However, given the severity of the situation and the likelihood that the capture of either figure would herald the end of any meaningful morale in the troops or civilian population, caution prevailed in this matter, with the cabinet and king evacuated further up to Northern England, along with the young Princess Elizabeth and her sister.
American forces, coupled with arriving Canadian forces, were rushed alongside British forces to the front. However, the grim nature of the war's precipitous decline for Allied fortunes reflected now in the understrength British Regiments, coupled with the lack of a Canadian supply line, only then compounded further by a relatively untrained and inexperienced American army and air corps, presented a grim picture for successful ejection of opposing forces. Whilst these difficulties were daunting, Allied commanders such as Field Marshal Bernard Montgomery and General Dwight D. Eisenhower pushed ahead with defensive lines, organising Commonwealth, American and various Free forces in exile from their occupied countries, in to relatively coherent fighting forces that could offer nominal and even considerable resistance to the oncoming Wehrmacht, even managing to achieve advances in East Sussex and Kent, trapping pockets of Wehrmacht infantry, whilst being unable to pin down the more mobile Panzers.
The situation in the air was slightly more favourable, as Spitfires, Hurricanes and P-40 Warhawk countered Bf 109's in the skies, though it found stiffer opposition against the Focke-Wulf Fw 190, yet still managed to hold out against the waves of aircraft, even with the German buildup of aircraft, fuel and pilots. This wouldn't last, with the range that the Luftwaffe had to fly cut considerably with the loss of airfields in the South of England as the campaign progressed, whilst airfields further along were mercilessly bombed until taken out of commission, cutting the range and availability of Allied aircraft considerably.
Aftermath
With the evacuation of Allied troops, the war in Europe came to an end. Most of The British Isles was placed under the collaborationist United Kingdom Of Great Britain, with Northern Ireland being given to The Republic Of Ireland. The once abdicated King Edward VIII would once again become the official Monarch Of Britain to give the newly formed state a sliver of legitimacy. Resistance against the occupation continued, with Her Majesty's Most Loyal Resistance including the Left Resistance fighting against the collaborationists and their German allies in the English insurgency.