World War II or the Second World War was a global conflict between two alliances: the Allies and the Axis powers. Nearly all of the world's countries—including all the great powers—participated, with many having invested all available economic, industrial, and scientific capabilities in pursuit of total war, blurring the distinction between military and civilian resources. Tanks and aircraft played major roles, with the latter enabling the strategic bombing of population centres and delivery of the only two nuclear weapons ever used in war. World War II was the deadliest conflict in history, resulting in 70 to 85 million fatalities, more than half of which were civilians. Millions died in genocides, including the Holocaust of European Jews, and by massacres, starvation, and disease. Following the Allied powers' victory, Germany, Austria, Japan, and Korea were occupied, and war crimes tribunals were conducted against German and Japanese leaders.
The Tehran Conference was a strategy meeting of Joseph Stalin, Franklin D. Roosevelt, and Winston Churchill from 28 November to 1 December 1943. It was held at the Soviet Union's embassy at Tehran in Iran. It was the first of the World War II conferences of the "Big Three" Allied leaders and closely followed the Cairo Conference, which had taken place on 22–26 November 1943, and preceded the 1945 Yalta and Potsdam conferences. Although the three leaders arrived with differing objectives, the main outcome of the Tehran Conference was the Western Allies' commitment to open a second front against Nazi Germany. The conference also addressed the Big Three Allies' relations with Turkey and Iran, operations in Yugoslavia and against Japan, and the envisaged postwar settlement. A separate contract signed at the conference pledged the Big Three to recognize Iranian independence.
The Yalta Conference, held 4–11 February 1945, was the World War II meeting of the heads of government of the United States, the United Kingdom and the Soviet Union to discuss the postwar reorganization of Germany and Europe. The three states were represented by President Franklin D. Roosevelt, Prime Minister Winston Churchill, and General Secretary Joseph Stalin. The conference was held near Yalta in Crimea, Soviet Union, within the Livadia, Yusupov, and Vorontsov palaces.
The Cairo Conference, also known as the First Cairo Conference, was one of 14 summit meetings during World War II, which took place on November 22–26, 1943. The Conference was held at Cairo in Egypt between China, the United Kingdom and the United States. Attended by Chairman Chiang Kai-shek, British Prime Minister Winston Churchill and US President Franklin D. Roosevelt, it outlined the Allied position against the Empire of Japan during World War II and made decisions about post-war Asia.
The European theatre of World War II was one of the two main theatres of combat during World War II. It saw heavy fighting across Europe for almost six years, starting with Germany's invasion of Poland on 1 September 1939 and ending with the Western Allies conquering most of Western Europe, the Soviet Union conquering most of Eastern Europe including the German capital Berlin, and Germany's unconditional surrender on 8 May 1945 although fighting continued elsewhere in Europe until 25 May. On 5 June 1945, the Berlin Declaration proclaiming the unconditional surrender of Germany to the four victorious powers was signed. The Allied powers fought the Axis powers on two major fronts, but there were other fronts varying in scale from the Italian campaign, to the Polish Campaign, as well as in a strategic bombing offensive and in the adjoining Mediterranean and Middle East theatre.
The final battles of the European theatre of World War II continued after the definitive surrender of Nazi Germany to the Allies, signed by Field marshal Wilhelm Keitel on 8 May 1945 in Karlshorst, Berlin. After German leader Adolf Hitler's suicide and handing over of power to grand admiral Karl Dönitz on the last day of April 1945, Soviet troops conquered Berlin and accepted surrender of the Dönitz-led government. The last battles were fought on the Eastern Front which ended in the total surrender of all of Nazi Germany’s remaining armed forces such as in the Courland Pocket in western Latvia from Army Group Courland in the Baltics surrendering on 10 May 1945 and in Czechoslovakia during the Prague offensive on 11 May 1945.
Operation Sledgehammer was an Allied plan for a cross-Channel invasion of Europe during World War II, as the first step in helping to reduce pressure on the Soviet Red Army by establishing a Second Front. It was to be executed in 1942 and acted as a contingency alternative to Operation Roundup, the original Allied plan for the invasion of Europe in 1943. Allied forces were to seize the French Atlantic ports of either Brest or Cherbourg and areas of the Cotentin Peninsula during the early autumn of 1942, and amass troops for a breakout in the spring of 1943.
The Cold War originated in the breakdown of relations between the two main victors in World War II: United States and the Soviet Union, and their respective allies, the Western Bloc and the Eastern Bloc, in the years 1945–1949.
Europe first, also known as Germany first, was the key element of the grand strategy agreed upon by the United States and the United Kingdom during World War II after the United States joined the war in December 1941. According to this policy, the United States and the United Kingdom would use the preponderance of their resources to subdue Nazi Germany in Europe first. Simultaneously, they would fight a holding action against Japan in the Pacific, using fewer resources. After the defeat of Germany—considered the greatest threat to the UK and the Soviet Union—all Allied forces could be concentrated against Japan.
The Western Front was a military theatre of World War II encompassing Denmark, Norway, Luxembourg, Belgium, the Netherlands, the United Kingdom, France, and Germany. The Italian front is considered a separate but related theatre. The Western Front's 1944–1945 phase was officially deemed the European Theater by the United States, whereas Italy fell under the Mediterranean Theater along with North Africa. The Western Front was marked by two phases of large-scale combat operations. The first phase saw the capitulation of Luxembourg, Netherlands, Belgium, and France during May and June 1940 after their defeat in the Low Countries and the northern half of France, and continued into an air war between Germany and Britain that climaxed with the Battle of Britain. The second phase consisted of large-scale ground combat, which began in June 1944 with the Allied landings in Normandy and continued until the defeat of Germany in May 1945 with its invasion.
Western betrayal is the view that the United Kingdom, France, and sometimes the United States failed to meet their legal, diplomatic, military, and moral obligations with respect to the Czechoslovak and Polish states during the prelude to and aftermath of World War II. It also sometimes refers to the treatment of other Central and Eastern European states at the time.
The Burma campaign was a series of battles fought in the British colony of Burma. It was part of the South-East Asian theatre of World War II and primarily involved forces of the Allies against the invading forces of the Empire of Japan. Imperial Japan was supported by the Thai Phayap Army, as well as two collaborationist independence movements and armies. Nominally independent puppet states were established in the conquered areas and some territories were annexed by Thailand. In 1942 and 1943, the international Allied force in British India launched several failed offensives to retake lost territories. Fighting intensified in 1944, and British Empire forces peaked at around 1 million land and air forces. These forces were drawn primarily from British India, with British Army forces, 100,000 East and West African colonial troops, and smaller numbers of land and air forces from several other Dominions and Colonies. These additional forces allowed the Allied recapture of Burma in 1945.
Operation Silver Fox from 29 June to 17 November 1941, was a joint German–Finnish military operation during the Continuation War on the Eastern Front of World War II against the Soviet Union. The objective of the offensive was to cut off and capture the key Soviet Port of Murmansk through attacks from Finnish and Norwegian territory.
The Allies, formally referred to as the United Nations from 1942, were an international military coalition formed during World War II (1939–1945) to oppose the Axis powers. Its principal members by the end of 1941 were the "Big Four" – the United Kingdom, United States, Soviet Union, and China.
The military history of the United States during World War II covers the nation's role as one of the major Allies in their victory over the Axis Powers. The United States is generally considered to have entered the conflict with the 7 December 1941 surprise attack on Pearl Harbor by the Empire of Japan and exited it with the 2 September 1945 surrender of Japan. During the first two years of World War II, the US maintained formal neutrality, which was officially announced in the Quarantine Speech delivered by US President Franklin D. Roosevelt in 1937. While officially neutral, the US supplied Britain, the Soviet Union, and China with war materiel through the Lend-Lease Act signed into law on 11 March 1941, and deployed the US military to replace the British forces stationed in Iceland. Following the 4 September 1941 Greer incident involving a German submarine, Roosevelt publicly confirmed a "shoot on sight" order on 11 September, effectively declaring naval war on Germany and Italy in the Battle of the Atlantic. In the Pacific Theater, there was unofficial early US combat activity such as the Flying Tigers.
The Soviet–Japanese War was a campaign of the Second World War that began with the Soviet invasion of Manchuria following the Soviet declaration of war against Japan on 8 August 1945. The Soviet Union and Mongolian People's Republic toppled the Japanese puppet states of Manchukuo in Manchuria and Mengjiang in Inner Mongolia, as well as northern Korea, Karafuto on the island of Sakhalin, and the Kuril Islands. The defeat of Japan's Kwantung Army helped bring about the Japanese surrender and the end of World War II. The Soviet entry into the war was a significant factor in the Japanese government's decision to surrender unconditionally, as it was made apparent that the Soviet Union was not willing to act as a third party in negotiating an end to hostilities on conditional terms.
Operation Overlord was the codename for the Battle of Normandy, the Allied operation that launched the successful liberation of German-occupied Western Europe during World War II. The operation was launched on 6 June 1944 (D-Day) with the Normandy landings. A 1,200-plane airborne assault preceded an amphibious assault involving more than 5,000 vessels. Nearly 160,000 troops crossed the English Channel on 6 June, and more than two million Allied troops were in France by the end of August.
The spring 1945 offensive in Italy, codenamed Operation Grapeshot, was the final Allied attack during the Italian Campaign in the final stages of the Second World War. The attack in the Lombard Plain by the 15th Allied Army Group started on 6 April 1945 and ended on 2 May with the surrender of all Axis forces in Italy.
The percentages agreement was a secret informal agreement between British Prime Minister Winston Churchill and Soviet leader Joseph Stalin during the Fourth Moscow Conference in October 1944. It gave the percentage division of control over Eastern European countries, dividing them into spheres of influence. It is also known as the naughty document, a nickname coined by Churchill himself due to his concerns regarding American reaction to any deal with such strong imperialist undertones, although in reality U.S. President Franklin Roosevelt was consulted tentatively and conceded to the agreement. The content of the agreement was first made public by Churchill in 1953 in the final volume of his memoir. The US ambassador Averell Harriman, who was supposed to represent Roosevelt in these meetings, was excluded from this discussion.
United States war plans for a conflict with the Soviet Union (USSR) were formulated and revised on a regular basis between 1945 and 1950. Although most were discarded as impractical, they nonetheless would have served as the basis for action had a conflict occurred. At no point was it considered likely that the Soviet Union or United States would resort to war, only that one could potentially occur as a result of a miscalculation. Planning was conducted by agencies of the Joint Chiefs of Staff, in collaboration with planners from the United Kingdom and Canada.
