Title: World War II
Content:  It is generally considered that in Europe World War II started on 1 September 1939, beginning with the German invasion of Poland and the United Kingdom and France's declaration of war on Germany two days later. The dates for the beginning of the war in the Pacific include the start of the Second Sino-Japanese War on 7 July 1937, or the earlier Japanese invasion of Manchuria, on 19 September 1931. Others follow the British historian A. J. P. Taylor, who held that the Sino-Japanese War and war in Europe and its colonies occurred simultaneously, and the two wars became World War II in 1941. Other starting dates sometimes used for World War II include the Italian invasion of Abyssinia on 3 October 1935. The British historian Antony Beevor views the beginning of World WarII as the Battles of Khalkhin Gol fought between Japan and the forces of Mongolia and 
Title: Political history of the world
Content:  World War II is generally considered to have begun on 1 September 1939, when Nazi Germany, under Adolf Hitler, invaded Poland. The United Kingdom and France subsequently declared war on Germany on the 3rd. Under the Molotov–Ribbentrop Pact of August 1939, Germany and the Soviet Union had partitioned Poland and marked out their "spheres of influence" across Finland, Romania and the Baltic states. From late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or controlled much of continental Europe, and formed the Axis alliance with Italy and Japan (along with other countries later on). Following the onset of campaigns in North Africa and East 
Title: World War II by country
Content:   The Empire of Japan was the leader of the Axis powers in the Pacific Theatre. Some scholars consider the outbreak of the Second Sino-Japanese War, which began when Japan invaded China after the Marco Polo Bridge Incident in 1937, to be the true beginning of World War II. This conflict merged with the world war following Japan's attack on Pearl Harbor in December 1941, which was immediately followed by a series of coordinated attacks on the U.S.-held Philippines, Guam and Wake Island; on the British colonies of Malaya, Singapore, and Hong Kong; and on the Kingdom of Thailand. During 1942 Japan launched offensives in the China, Southeast Asian, and Pacific Theatres of the war. By late 1942 Japan was on the defensive as the Allies reversed its earlier gains. The Atomic bombings of Hiroshima and Nagasaki by the United States, together with the declaration of war by the Soviet Union, convinced the Japanese government to surrender unconditionally on September 2, 1945. Many political and military leaders from Japan were convicted for war crimes before the Tokyo tribunal and other Allied tribunals in Asia.
Title: World War II
Content:  World War II or the Second World War, often abbreviated as WWII or WW2, was a global war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing military alliances: the Allies and the Axis powers. In a total war directly involving more than 100 million personnel from more than 30 countries, the major participants threw their entire economic, industrial, and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. Aircraft played a major role in the conflict, enabling the strategic bombing of population centres 
Title: World War II
Content:  Soviet Union from May to September 1939. Others view the Spanish Civil War as the start or prelude to World War II. The exact date of the war's end is also not universally agreed upon. It was generally accepted at the time that the war ended with the armistice of 14 August 1945 (V-J Day), rather than with the formal surrender of Japan on 2 September 1945, which officially ended the war in Asia. A peace treaty between Japan and the Allies was signed in 1951. A 1990 treaty regarding Germany's future allowed the reunification of East and West Germany to take place and resolved most post-World WarII issues. No formal peace treaty between Japan and the Soviet Union was ever signed, although the state of war between the two countries was terminated by the Soviet–Japanese Joint Declaration of 1956, which also restored full diplomatic relations between them.
Title: Timeline of World War II (1939)
Content:  This is a timeline of events of World War II in 1939, from the start of the war on 1 September 1939. For events preceding September 1, 1939, see the timeline of events preceding World War II. Nazi Germany's invasion of Poland on 1 September 1939, and Britain and France's declaration of war on Germany two days later marks the beginning of World War II. After the declaration of war, western Europe saw very little land or air active military confrontation at first, and the period was termed the "Phoney War". In eastern Europe, however, the agreement between the Soviet Union and Nazi Germany signed on 23 August opened the way in September for the Soviet Union's invasion of eastern Poland, which was divided between the two invaders before the end of the month. The Soviet Union starts a new military offensive by invading Finland at the end of November. 1939: September·October·November·December·
Title: Western Front (World War II)
Content:  On 1 September 1939, World War II began with the German invasion of Poland. In response, Britain and France declared war on Germany on 3 September. The next few months in the war were marked by the Phoney War.
Title: Interwar period
Content:  The interwar period ended in September 1939 with the German and Soviet invasion of Poland and the start of World War II.
Title: Timeline of World War II (1939)
Content: 1: The Republic of China and the Empire of Japan are involved in the early stages of the third year of armed conflict between them during the Second Sino-Japanese War. The war is in what will be known as the "Second Period", which starts after the fall of Wuhan in October 1938 and ends in December 1941 with Pearl Harbor. This conflict will eventually be swept up into World War II when Japan joins the Axis and China joins the Allies. 1: The invasion of Poland by Germany starts at 4:45 a.m. when the Kriegsmarine's battleship Schleswig-Holstein opens fire on the 
Title: Pact Ribbentrop - Beck
Content:  The author writes that by Poland not opposing Adolf Hitler in September 1939, the Second World War starts on April 9, 1940 by a German attack on Western Europe. After capturing Paris and defeating Belgium, the Netherlands, Norway, Denmark and France, on June 21, 1941, the Wehrmacht, together with the Polish Army, invades the Soviet Union. By the winter of 1941-1942, the Soviet Union ceases to exist. Poland and Germany divide its territory, but soon, mutual relationships deteriorate. Meanwhile, Germany keeps fighting the United Kingdom and the United States. The war is costly, and by 1944, all of the main units of the Wehrmacht are in 

Question: when did world war 2 officially start and end?
Answer: 1939.
1945.
2 September 1945.
1 September 1939.