When war broke out, Germany swept through Europe during the Blitzkrieg, gaining military control of countries rapidly. The capture of France on June 14th, 1940 left Britain a sole island nation fighting against Nazi Germany. As an island, Britain relied on the sea for defence. German operation Sealion planned to land German forces to capture Britain; in order to safely transport troops, Germany needed to control the sea. At the same time, Britain was importing supplies across the Atlantic from America, which kept them alive through the war. The need for control on the sea was underpinned by looming threat from the Germans, and the necessity of trade between the Allies. Britain needed to import weapons and supplies from America, as the Germans attacked these trade routes the Battle of the Atlantic begun. The battle of the Atlantic was fought between 1939 until the end of the war in 1945. It was the longest battle in WW2, and victory would ensure the survival of Britain. Germany attempted to cripple the British navy through the use of undetectable U-boats, which sank thousands of Military and trade ships in an attempt to weaken the British navy and starve them to surrender. But for the British, the sea was too important to lose. At the beginning of the war, there were no reliable methods for avoiding U-Boats, so allied ships were at the mercy of luck, so much so that Winston Churchill said: “the only thing that really frightened me was the U-Boat peril”. But by 1941 the enigma was cracked, Britain now knew where U-Boats were headed and could steer convoys away from danger, saving 105 out of 174 convoys between may 1942 and may 1943. Furthermore, technological advancements led to the creation of depth charges which helped the British to combat the U-boats. As well as the production of the Hedgehog anti-submarine weapons destroyed many German naval resources. This kept trade between Britain and America going, ensure vital goods like food and munitions reached Britain keeping them alive. Britain’s contribution to the war at sea had considerable importance as it led to naval dominance in the Atlantic. If Germany had have controlled the Atlantic, the D-day invasion would have been nearly impossible to bring to fruition. Defeat in the Atlantic meant almost certain defeat for Britain and their resistance. And would have damaged Russia’s defence in the east, due the destruction of German U-Boats forced Hitler to draw more resources from the Eastern Front where Hitler desperately needed them.Britain not only had to fight the German Navy, they had to compete with the German Air Force. With the invention of modern aircrafts, factories and towns could be destroyed by bombers. Germany planned to cripple the British air force, allowing them to destroy the ports in order to launch a full-scale invasion. To stop the Germans Britain had to control the air. The war began poorly for Britain. They were marred by the defeat at Dunkirk, the evacuation of 343,000 soldiers from the beaches of France. It was a complete military failure; the British lost 1954 of its artillery and 615 tanks, leaving them to be captured or destroyed by the Germans. Yet it was a Symbolic success for Britain, the boats of the British saved the soldiers and led to the British resilience that came to be known as ‘Dunkirk spirit’. This was integral in allowing the British to persevere through the Battle of Britain. The Battle of Britain signified the end ofthe phoney war, the period in which the British were at war with the Germans but did not fight. The Germans planned to invade Britain, and Hitler’s generals were worried about the damage that the Royal Air Force could inflict on the German Army during the invasion. Because of this Hitler agreed that the invasion should be postponed until the British Air Force had been destroyed. The German campaign objective became gaining air superiority over the RAF, especially Fighter Command. They began with the bombing of aircraft bases across Britain. This was less effective than the Germans had hoped; Britain had built up its air defences since 1936 under air chief marshal Sir Hugh Dowding. The widespread use of radar alerted the RAF of incoming Luftwaffe and allowed for a quick defence. Britain was outshooting and outproducing the Germans. Germany couldn’t destroy all the air force bases and In September 1940 Germany shifted their targets to bomb cities. This was terrifying for civilians, claiming over 32,000 lives and injuring over 80,000 more, But it gave the RAF the ability to rebuild their planes. They were able to put an end to the German air raids, and the Battle of Britain signified the first loss of the German army. The defence against the German Luftwaffe was integral to the survival of Britain, which in turn became a base of future attacks on Germany. Had Britain lost to the Germans, Britain would have fallen, and the base of D-day operations would be under Nazi control. The victory ensured that Germany have would fight a war on two fronts.The success at the Battle of Britain also allowed Britain to launch aerial attacks, with the USA, against Germany. These attacks continued throughout the war. It was a controversial tactic. While British aerial attacks were not very effective, only 1 in 100 bombs landed five miles within its target, and the prediction that bombing cities would break the German morale was false. carpet bombing was extremely effective in large cities such as Hamburg, where thousands of deaths and the destruction of over 4000 factories occurred. The damage caused by these attacks crippled the German industrial might and forced resources and troops away from the Eastern Front, 2/3 German planes had to protect German cities. The bombings also destroyed German coastal defences and allowed for D-day plans to be made, opening a second front for the already stretched Germans. However, Britain was not alone. America produced the most machinery during the war, they produced 300,000 planes and supplied both Britain and Russia with planes to cover their losses in combat. As well as supply Britain money to build their own planes through lend-lease. They also took the brunt of the losses in the bombing campaign because they bombed during the day to ensure they struck their target. While this caused a better success rate of missions, it led to far more American deaths. The bombing campaign did not win the war, but it aided in the invasion of Germany.If Germany had not been invaded, the war would have continued. To destroy the Nazi forces, Berlin would have to be captured. All three of the Allies would open fronts against the Germans in the East and West. With Russia suffering the most casualties at 29 million. On land, Britain made two major contributions in the war. The first British contribution on land was in the North African campaign against the Afrika Korps led by Rommel. Britain had lost much of its territory due to Rommel’s advance across North Africa in late 1942. But the British victory of the Battle of El Alamein in November 1942 was an important victory for the British campaign in Africa. It blocked Hitler’s access to the oil fields. The North Africa campaign was seen as insignificant to the Germans, but it led to the invasion of Southern Italy, and the fall of Italy as an axis power. It was a large blow to Germany, they stood against the combined forces of the Allied powers. However, Germany put little resources into the Africa campaign, with only four divisions under the control of Rommel.The second contribution from Britain was D-day. Britain helped retake France from the German army. On 6 June 1944, Britain landed on the Beaches of Normandy, for the biggest land campaign of the western front. Britain was instrumental in the planning of D-day; they disrupted the German intelligence, making Hitler believe the invasion would begin at France’s Pas de Calais region 150 miles northeast of Normandy. Britain was the launch point of the invasion, and if Britain had fallen in the war D-day would be impossible. However, Britain was not alone. For the initial invasion, they only attacked two out of the five beaches and sent 14 divisions, compared to the USA’s 23 divisions. And by the end of the war, the number of British soldiers decreased on the Western Front, whilst America’s grew to 60 divisions.