1941: The war becomes global

Europe

11 March President Roosevelt signs the Lend-Lease Act. This program was the first large step away from American isolationism. Historians estimate that payments to the major recipients included about $14 to $20 billion to Britain; $9-10 billion to the Soviet Union; France, $3.5 billion; and China and India, $2.2 billion, for a total of $48 billion.

Yugoslavia's government succumbed to the pressure of Italy and Germany and signed the Tripartite Treaty on 25 March 1941. This was followed by anti-Axis demonstrations in the country and a coup which overthrew the government and replaced it with a pro-Allied one on 27 March 1941. Hitler's forces then invaded Greece and Yugoslavia on 6 April 1941. Hitler reluctantly sent forces to assist Mussolini's forces in their attempt to capture Greece, principally to prevent a British build-up on Germany's strategic southern flank. With these new troops the Axis succeeded in driving the Greek forces back.

The German battleship Bismarck sailed on her first and only mission, codenamed Rheinübung, on 18 May 1941. She sank the HMS Hood in the Battle of the Denmark Strait before being scuttled at sea on 24 May after having been crippled by an unlucky torpedo hit, then caught and pummeled to a wreck by British battleships HMS King George V and HMS Rodney.

On 20 May 1941, the Battle of Crete began when elite German Fallschirmjäger and glider-borne mountain troops launched a massive airborne invasion of the Greek island. Crete was defended by Greek, New Zealand, Australian and British troops. The Germans attacked the island simultaneously on the three airfields. Their invasion on two of the airfields failed, but they successfully captured one, which allowed them to reinforce their position and capture the island in a little over one week.

On 22 June 1941 Operation Barbarossa, the German invasion of the Soviet Union, the largest invasion in history, began. German armies advanced rapidly deep into the Soviet Union, while Soviet forces fought a war of scorched earth, dismantling as much industry as possible and moving it to the Ural mountains for reassembly. By December the German Army had reached a line at the gates of Leningrad, Moscow, and Rostov, at the cost of about 23 percent casualties, while almost the entire western Soviet army had been destroyed in huge battles of encirclement. The Germans however had badly under-estimated the size of the overall Soviet army and were now dismayed by the presence of new forces, including fresh Siberian troops under General Zhukov, and by the onset of a particularly cold winter. The Germans were stopped literally within sight of Saint Basil's Cathedral which is inside the Kremlin in Moscow, then forced to pull back, the first German defeat of World War II.

The Continuation War between Finland and the Soviet Union began with Soviet air attacks shortly after the beginning of Operation Barbarossa, on 25 June, and ended with an armistice in 1944.

The Atlantic Charter was issued as a joint declaration by British Prime Minister Winston Churchill and U.S. President Franklin D. Roosevelt, at Argentia, Newfoundland on 14 August 1941.

Germany declared war on the United States on 11 December 1941, following the Japanese attack on Pearl Harbor, even though it was not obliged to do so under the Tripartite Pact of 1940. Hitler made the declaration in the hopes that Japan would support Germany by attacking the Soviet Union. Japan did not oblige and this diplomatic move by Hitler proved a catastrophic blunder giving President Roosevelt the pretext needed for the United States to join the war in Europe with full commitment and with no significant opposition from Congress. Some historians mark this moment as another major turning point of the war as Hitler provoked a grand alliance of the largest empire (the British Empire), the largest military (the USSR), and the largest industrial base (the USA). The combined resources of these countries made it possible to wage powerful offensives against the Axis in many parts of the world simultaneously.

In late December 1941 Churchill met with Roosevelt again at the Arcadia Conference, which lasted three weeks. They agreed that defeating Germany had priority over defeating Japan. The Americans proposed a 1942 cross-channel invasion of France which the British strongly opposed, suggesting instead a small invasion in Norway or landings in French North Africa. The Declaration by the United Nations was issued.

The Mediterranean

Operation Sonnenblume - Rommel's forces advanced rapidly eastward, laying siege to the vital seaport of Tobruk. An Axis offensive captured the city (see Battle of Gazala) then drove the Eighth Army back to a line at El Alamein.

The Middle East

In June 1941, Allied forces invaded Syria and Lebanon, capturing Damascus on 17 June (see Syria-Lebanon campaign).

In August, British and Soviet troops occupied neutral Iran (see Operation Countenance) in order to secure its oil and a southern supply line to Russia.

East Asia and the Pacific

Japan planned an attack on Pearl Harbor to cripple the U.S. Pacific Fleet before consolidating oil fields in the Dutch East Indies. On 7 December 1941, a Japanese carrier fleet carried out a surprise air attack on Pearl Harbor, Hawaii. The raid resulted in eight battleships either sunk or damaged, however, the attack failed to sink any aircraft carriers, nor damage Pearl Harbor's usefulness as a naval base. The attack united public opinion in the United States against Japan.

The following day, 8 December 1941, the United States declared war on Japan. On the same, day, China officially declared war against the Japanese Empire.

Simultaneously, Japan also attacked the Philippines. It soon invaded the Philippines and also the British Colonies of Hong Kong, Malaya, Borneo, and Burma, with the intention of seizing the oilfields of the Dutch East Indies. Despite fierce resistance by British, Canadian, and Indian forces, all these territories capitulated to the Japanese in a matter of months. The British island fortress of Singapore was captured in what Churchill considered one of the most humiliating British defeats of all time.