A timeline of WWII, one of the most devastating conflicts in world history

In September 1939, German tanks roll through Poland in a lightning-fast offensive that bombs and destroys much of the country's landscape and infrastructure. The invasion prompts the United Kingdom and France to declare war on Germany.

In anticipation of Germany's likely attempt to cut Great Britain off from its overseas food and goods supply, Great Britain introduces rationing in January 1940. Each household receives a ration book that dictates how much they can buy. Before the war, Britain imported 55 million tons of food per month—a month after the war begins, the figure plummets to 12 million.

In the span of two months in the spring of 1940, the Germans conquer an astonishing number of countries thanks to their blitzkrieg tactics of fast-moving tanks and relentless aerial bombardment. Hitler's troops overwhelm the armies of the Netherlands, Belgium, France, Denmark, Luxembourg, and Norway in the months of April and May alone.

British troops delay the German advance, but they can't stop it, holding out in Dunkirk, a port city in Northern France. Using hundreds of naval and civilian vessels to cross the English Channel, the Allies, including the British Expeditionary Force and a smattering of Polish and French forces, retreat from Dunkirk to England as German forces close in.

The Nazis are finally stopped in their relentless drive to conquer Europe in the Battle of Britain that lasted from July through October of 1940. From July through September, the British hold off an intense bombardment from the fearsome German Air Force, which prevents a German attempt to invade the British Isles, and allows the nation to serve as a holdout for Allied hopes.

Although they fail in the Battle of Britain, that doesn't stop the German Air Force—called the Luftwaffe—from trying to undermine the British. In September 1940, this takes the form of nighttime bombing raids on the city of London, which continue for 56 of the next 57 days. The bombings persist until May 1941.

Operation Barbarossa was the German Army's code name for its planned invasion of the Soviet Union. But things don't go exactly according to plan. When Germany fails to subjugate the Soviets, they find themselves fighting a dreaded two-front war for the first time, defending territory in both Europe's east and the west, while getting sucked into Italy's war in North Africa.

When Axis power Japan bombs Pearl Harbor in Hawaii on the morning of Dec. 7, 1941, the United States officially joins World War II, declaring war on Japan, Germany, and Italy. The sneak attack on America's Pacific fleet kills more than 2,400 Americans and leaves another 1,000 wounded.

Axis power Japan conquers the lightly defended British colony of Singapore on Feb. 15, 1942. A major Axis victory, Singapore surrenders to the Japan general in charge of the campaign in front of Japanese news cameras. Winston Churchill famously calls the fall of Singapore "the worst disaster and the greatest capitulation in British history." In total, 130,000 allies are taken as prisoners and kept on starvation rations while being forced into labor camps, most notably the Thai-Burma Railway.

The decisive point in the Pacific campaign comes just six months after Pearl Harbor, when the Americans defeat the Japanese Navy at Midway. Thanks to major advances in code breaking, the U.S. forces know the Japanese plan ahead of time, debilitate Japan's naval forces in this crucial battle, and momentum in the Pacific now swings to the Allies.

Many historians pinpoint the Soviet defense of Stalingrad as the war's pivotal turning point. The failure of the German Army to take the city, which leads to the complete surrender of the Sixth Army, is its first catastrophic failure, and marks the point after which a German victory in the east becomes infeasible. The battle lasted from Aug. 23, 1942, to Feb. 2, 1943.

In autumn of 1942, with the Axis powers already controlling Libya, Egypt was at risk of falling next when the pivotal Second Battle of El Alamein begins. The British and their allies hold off the Germans at the decisive battle, which ends in November and turns the tide against the Axis in North Africa.

The British and Americans collaborate for the first time on an invasion plan to take North Africa back from the Axis powers. Called Operation Torch, the amphibious assault captures Morocco and Algeria, controlled by the collaborationist Vichy French Petain regime, and opens a second, Western front in the North African theater.

What remains of the German Sixth Army in Stalingrad surrenders on Jan. 31, 1943. Over 333,000 German soldiers had been sent to take the city and only 90,000 remain alive. Friedrich Paulus, commander of the Sixth Army, becomes the first Field Marshal in Germany's history to ever surrender. While the Germans desperately cling to their gains in Russia and even manage a few ultimately unsuccessful counter-offensives, the Stalingrad surrender marks a turning point in the east from which Germany never recovers.

From their bases in recaptured North Africa and Sicily, the Allies invade Italy's mainland. The Allies had already taken the island of Sicily earlier in the summer, and a demoralized Italian government secretly agrees to surrender the very day the Allies land on the mainland.

In stark contrast to the campaigns against London several years prior, the Royal Air Force, now joined by their American allies, takes the battle to Berlin in late fall 1943. The Allies had bombed Berlin before, but never on this scale: They inundate the city with bombs for months. The Kaiser Wilhelm Memorial Church, heavily damaged in the raids, remains unfixed to this day as a memorial of the war.

In one of the most famous military battles in history, Allied forces, led by the Americans, capture several beaches in Normandy, France, on June 6, 1944, bringing the fight to French soil after three years of Nazi occupation. More than 9,000 American troops lose their lives on this day, but the campaign marks the beginning of the end for Hitler, whose troops, save a couple of unsuccessful offensives like the famous Battle of the Bulge, remain on the defensive for the rest of the war. The Allies liberate Paris two months later.

As German territory is progressively liberated from the east by the Soviets, the horrors of the Nazi concentration camps come to light. When the Soviets liberate Auschwitz in Poland in January 1945, an estimated 1.1 million people, mainly Jews, have been murdered there.

Barricaded in a bunker in Berlin with Soviet troops closing in, Hitler shoots himself at the end of April 1945. A week later, his deputy Karl Donitz unconditionally surrenders to the Allies.

In August 1945, the United States drops two atomic bombs on Hiroshima and Nagasaki in Japan. Precise casualty reports are difficult to come by because of the devastation the bombs wrought, but it's believed hundreds of thousands of civilians die. The Japanese government unconditionally surrenders after the bombings, thereby ending World War II.