Many in Japan -- including most of the nine former prime ministers whom Japanese Emperor Hirohito met with a week prior to the attack -- had opposed it. Yet Gen. Hideki Tojo's government authorized the attack with the objective of destroying the US Pacific Fleet, which potentially could have blocked Japan's access to the resources of Southeast Asia.

The Pearl Harbor attack, however, was only partly successful. Though Japanese forces caused significant damage to the US Fleet and killed 2,335 US troops and 68 civilians, their attack was not fatal. The Fleet's three aircraft carriers weren't in Pearl Harbor when the attack occurred and many of the damaged ships and planes were able to be repaired. This would come back to haunt Japan the next June, when US forces, including two of those carriers, took out four Japanese carriers at the Battle of Midway and turned the Pacific war in the US favor.

The Japanese attack had given President Roosevelt the pretext he sought to bring the US into the war. Americans may have overwhelmingly favored the Allies over the despised Nazis and sympathized with the plight of Chinese being brutalized by Japan, but few wanted to get drawn into another war. World War I had left a bitter taste in their mouths. Not only had it not been "the war to end all wars" or the war to make the world "safe for democracy," it had enriched the greedy bankers and arms manufacturers -- the "merchants of death" as they were then known -- and done nothing to end colonial exploitation.

By 1941, Roosevelt surreptitiously maneuvered the US into confrontations with both Germany, which had conquered much of Europe, and Japan, which had seized Manchuria and Indochina and was waging a vicious war against China. At Newfoundland in August 1941, he told Churchill that he "would wage war, but not declare it" and do everything he could to "force an 'incident' that could lead to war." His overt support for Britain against Germany and decision to halt desperately needed exports of oil, metal, and other resources to Japan proved sufficient.

One day after the attack on Pearl Harbor, Roosevelt addressed Congress, which approved his war resolution with one dissenting vote. Three days later, Germany and Italy, Japan's allies, declared war against the United States.

The world would never be the same. But here's how it could've been different.

US and Japan on a collision course for years

The attack on Pearl Harbor has loomed large in the American imagination for several reasons.

But had the Japanese not attacked Pearl Harbor, the Pacific War would largely have evolved along similar lines. The US and Japan had been on a collision course for months if not years. With or without the attack on Pearl Harbor, the two countries were heading for war.

What most Americans forget is that it was not only Pearl Harbor that Japan attacked on December 7, 1941. As Roosevelt told Congress on December 8, Japan had also attacked the British colonies of Hong Kong and Malaya, the US colony in the Philippines, and US holdings in Guam, Wake Island, and Midway Island. The attack on Malaya actually preceded the assault on Pearl Harbor by more than an hour. In addition, though not mentioned by Roosevelt, Japan invaded Thailand. It also attacked Singapore, which was then part of British Malaya.

US officials had broken Japanese diplomatic codes in August 1940, enabling them to monitor Japan's war planning. They knew an attack was coming. They just didn't think it was coming at Pearl Harbor. The most likely targets in their minds were the oil-rich Dutch East Indies (Indonesia), Malaya, and the Philippines.

Soviets deserve lion's share of the credit for victory in Europe

While US involvement was absolutely crucial to Allied victory in the Pacific War, it was less so in the defeat of the European Axis powers. In fact, had the US not entered the European war, the outcome would have been the same. By the time the US and Britain finally initiated their promised second front in France a year and a half after Roosevelt publicly announced it would begin, the Russians had already turned the tide and German forces were in full retreat across Europe.

Up to that point, the US and British had been confronting some 10 German divisions combined while the Soviets were confronting nearly 200 by themselves. Forcing Germany to fight on two fronts certainly expedited the end of the war, but it didn't change the outcome.

Contrary to American mythology, the Soviets deserve the lion's share of the credit for victory in Europe. And they suffered immensely in bringing this about. In quantitative terms, the 27 million Soviets who died at the hands of Germany is the equivalent of one 9/11 a day every day for 27 years. It is the equivalent of one Pearl Harbor a day every day for 30 years.

Despite Churchill's hatred of Bolshevism, the British owe a huge debt of gratitude to the Soviets, without whom they might be speaking German today. They also owe a huge debt to the Americans without whom they might be speaking Russian.

It is interesting to contemplate how the face of Europe would have been different if the US had remained the "arsenal" of the Allied powers without actually joining the war. It was fortuitous that Germany and Italy declared war against the US on December 11, 1941 without which Roosevelt would have had to find another justification for American entry.

Where would the line between the Soviets and the West have been drawn if the US had not entered the European war? How might the Soviet economy have developed if Soviet leaders had access to the greater potential wealth of West Germany and France? Might socialism have appeared a more viable option in the postwar world if the US was not in a position to help rebuild the depression- and war-shattered capitalist economies?

What if Roosevelt had kept Henry Wallace as vice president?

There are some other interesting counterfactuals that can be explored regarding the Second World War, some of which we do look at in our documentary film and book series The Untold History of the United States.

What would have happened if Roosevelt had retained his visionary and controversial vice president Henry Wallace on the ticket in 1944 instead of the much smaller minded Harry Truman?

Despite the opposition of the conservative Democratic Party bosses, Roosevelt had the moral authority and political muscle to insist upon Wallace remaining on the ticket as his wife and children and the majority of Americans desired.

The Gallup Poll -- a US public opinion survey -- released on July 20, 1944, the first day of the Democratic Party convention in Chicago, reported that 65 percent of potential Democratic voters wanted the enormously popular Wallace back on the ticket as vice president. Two percent wanted Truman. The internal machinations that resulted in Truman's selection are a sordid tale with which few Americans are familiar.

Had Wallace become president upon Roosevelt's death in April 1945 instead of Truman, there would have been no atomic bombings of Japan and possibly no Cold War.

Wallace envisioned friendship between the Americans and the Soviets and a healthy competition between the two systems in which each would strive to show that it was better suited to serve the needs of humanity. He would have delivered on the $10 billion credit that Roosevelt had dangled before the Soviets to help them rebuild from a war that had turned much of the country into a wasteland. The positive repercussions that might have had in Soviet-occupied Europe are incalculable.

It is also worth noting that Wallace was a fierce opponent of colonialism, who openly deplored the British and French empires, leading Churchill and the French to pressure Roosevelt to replace him on the ticket. Roosevelt largely shared Wallace's views regarding empire. He condemned British rule in Gambia, calling it "the most horrible thing I have ever seen in my life." He felt similarly about Dutch exploitation of the East Indies and French rule in Indochina, insisting he would not let the French back in after the war.

On some level, he understood that the Pacific War was rooted in imperial rivalries, commenting privately, "Don't think for a minute that Americans would be dying in the Pacific...if it hadn't been for the short-sighted greed of the French and the British and the Dutch." He promised "immediate" independence for the Philippines once Japanese troops were ousted shortly before his death.

Roosevelt often wavered on this issue, but Wallace never did. He was steadfast in his hatred of colonial exploitation and the racism that justified it. Think of the lives that could have been saved and the misery that could have been avoided if colonialism had been ended peacefully in the immediate aftermath of the war.

The world without the atomic bombings

A second counterfactual is what would have happened if World War II had ended without the atomic bombs being used on Hiroshima and Nagasaki in Japan?

American mythology holds that the two bombs ended the war and, by obviating the American invasion of Japan, humanely saved millions of American and Japanese lives. According to defenders of the atomic bombing, the cost, by 1950, of 200,000 dead in Hiroshima and 140,000 dead in Nagasaki was a small price to pay.

The evidence is overwhelming, as we show in Untold History, that it was the Soviet invasion of Manchuria, South Sakhalin, the Kurile Islands, and Korea, which began at midnight on August 8, 1945 that precipitated the Japanese surrender and not the atomic bombs.

US intelligence had been forecasting such an outcome for months and Truman acknowledged that the Soviet entry would be decisive. At Potsdam on July 17, he wrote in his diary, Stalin "will be in the Jap war on August 15. Fini Japs when that comes about." He characterized the intercepted July 18 cable as "the telegram from the Jap emperor asking for peace." He knew the end was near and the bombs weren't necessary.

If the bombs had not been used in the war, might the US and the USSR have avoided the nuclear arms race that the atomic bombings set in motion? Soviet leaders, knowing full well that the bombs weren't needed to defeat Japan, interpreted their use as a warning of the devastation that the US would wreak on the Soviets if they interfered with US postwar plans. We've lived with the threat of the extinction of life on this planet ever since.

Japan's fate was sealed when the Soviets invaded as the official US Navy Museum in Washington, DC acknowledges. The Japanese hurried to surrender to the Americans while they still had the chance, knowing that a Soviet takeover would spell the end of not only the emperor system but of the capitalism that supported it. At first, the US occupation was relatively benign and in some ways even enlightened. The US imposed Japan's peace constitution, which disavowed the sovereign right of war and disallowed the retention of offensive military forces. It is those forward-thinking principles that the Shinzo Abe administration is presently trying to eviscerate.

If the Soviets had had a greater hand in the occupation, Japan might have become a Cold War battleground as Korea did. Would the Russians have been torn between the conflicting pressures to rebuild Japan and to loot it that they faced in Germany? The animosity they felt toward the Japanese paled in comparison to their hatred and mistrust of the Germans, who had so much Soviet blood on their hands. As we know, the US quickly abandoned its progressive vision for postwar Japan and sought to rebuild it as the military and economic outpost of Western capitalist interests in the volatile Asia-Pacific region. Either way, Japanese cars, electronics, and sushi were fated to transport, connect, and feed the planet. The world would be better off, however, if the rise of Japanese militarism could have been thwarted or further delayed.

World War II with its vast bloodletting, incredible toll of human life, deployment of technology to maximize killing and destruction, and prominent display of the ugly side of human nature, replete with racism, xenophobia, and ethnic and religious bigotry, serves as a cautionary tale of what happens when we unleash the forces of fear, hatred, and nationalism.

Some of those same forces are rampant in the world today. Pearl Harbor should serve as a reminder. But we must be careful to draw the right lessons to avoid a repeat of the horrors that engulfed the planet more than 75 years ago.