General Erwin Rommel, “the Desert Fox,” was reputedly the best tactician in the entire German Army. For years, he led his panzers across multiple campaigns in North Africa.

But what was a German army doing zipping across the deserts of Libya?

Simple: Rommel was trying to capture the Suez Canal, and with it the route to the precious, untapped oil fields of the Middle East.

From the deserts of North Africa to the icy waters of the Atlantic Ocean, the jungles of the South Pacific and the skies above Romania, World War II was defined by a struggle over a single resource - petroleum.

Without oil, modern mechanized warfare was impossible. It fueled the war effort of each major power, and battles over access and control of petroleum resources marked the war’s most important episodes—from the Battle of Stalingrad to the attack on Pearl Harbor.

Hitler’s Dilemma

German fuhrer Adolf Hitler rose to power in the 1930s in the wake of the Great Depression - a cataclysmic economic crisis that affected the entire world, but which hit Germany especially hard. Amidst spiraling inflation and mass unemployment, Hitler preached a return to national greatness through conquest. Germany would dominate Europe, and in so doing capture all the resources it would need to become a self-sustaining, self-sufficient economic power.

Despite being one of the most powerful industrial nations on earth, Germany had no oil reserves. Furthermore, it lacked an empire - like the British - that would give it access to oil overseas.

In fact, in the 1930s oil production was dominated by a handful of countries—the United States, which accounted for 50% of global oil production, as well as the Soviet Union, Venezuela, Iran, Indonesia, and Romania.

But in order to fuel its industrial economy and power its growing war machine, Germany would need oil reserves - as German oil production was negligible.

Hitler had two choices: either it get by on alternatives - such as producing synthetic oil from coal, which Germany had in abundance - or secure oil through conquest.

Thus, the war in Europe was often fought over petroleum, which Hitler needed to build and sustain the German empire.

After the fall of France in May 1940, Hitler’s only adversary was Great Britain. With a powerful navy and a sprawling international empire (two things Germany lacked), Britain was in a strong position to oppose Hitler, though its ability to intervene on the European continent was limited.

Britain, like Germany, had no oil reserves. It depended on supplies from overseas, particularly oil from the United States and Venezuela. Oil tankers made easy targets for German U-boats, which waged their undersea war with the Royal Navy and the British merchant fleet. Related: Building The World’s Largest Battery

While Britain took tremendous losses, particularly in the Spring of 1941 and 1942, eventually the Royal Navy was able to manage the U-Boat threat.

On June 1941, a vast German army invaded the Soviet Union. One wing advanced towards Leningrad, another towards the Soviet capital at Moscow. A third army group cut through the south, slicing through the Ukraine. It’s objective: the Soviet oil fields in the Caucasus Mountains.

The Battle of Stalingrad, the turning point for the war on the Eastern Front, came after the German army made a push towards the Caucasus Mountains - the heart of the Soviet oil industry. Capturing the refineries and oil fields around Baku would have given Hitler the oil he needed to fuel the German economy and war-machine.

But the German advance was turned back at Stalingrad. After the initial shock of the invasion, the Soviet army recovered its strength and began pushing the German forces from Russia.

Hitler’s armies failed to secure access to Russian oil, and in 1943 began a slow retreat, beaten back by overwhelming Soviet forces.

Bleeding Germany Dry

Britain and the United States, meanwhile, were preparing for Operation Overlord - the invasion of German occupied-France. But before landing troops, the Allies conducted a massive bombing campaign of German industries, cities and military installations.

Thousands of British and American bombers flew thousands of sorties in 1942-1944. Bombing strategy was still in its infancy, and not all the Allied bombing runs were successful - in fact, Germany was producing more planes and tanks in late 1944 than it had been in 1942, despite the heavy bombing.

But in one important way, the Allied bombing was decisive. In 1943 and 1944, British and American planes targeted the Ploesti oil fields in Romania, a German ally. Romania was Hitler’s major source of oil, since he had failed to conquer the Russian fields.

The Allied bombers had trouble hitting the oil fields and refinery - like other bombing raids in WWII, the majority of the bombs failed to hit their targets. But the sheer number of sorties left a mark. By June 1944, German access to oil had been seriously impaired - and the results were devastating.

The Luftwaffe, Germany’s mighty air force, was grounded. Panzer divisions couldn’t maneuver for fear of using up precious oil. German army units lacked mobility and couldn’t respond quickly when the Allied armies arrived on the shores of Normandy. Lack of fuel crippled the German army.

In Summer 1944, led by the Third Army of General George S. Patton, the Allies swept across France, driving Hitler’s forces back to the Rhine River. But in August, the advance suddenly halted. Patton had gone so far, so fast, he had exceeded his supply lines.

Now it was the Allies who were running low on fuel: the huge Anglo-American army was poised to invade Germany, but it lacked the gas to launch an all-out offensive.

Instead, it was the German army that would make the next move. In December, as the Allied armies dug in to await re-supply, Hitler sent what was left of his Panzer divisions to strike the Allied over-stretched lines in the Ardennes Forest of Belgium.

The German objective wasn’t the forest - it was the port city of Antwerp, far behind Allied lines, and the only port from which the Allies could be re-supplied.

If they could take Antwerp, Hitler would be able to deprive Eisenhower of the gasoline his armies would need to push on into Germany - potentially changing the course of the war.

But the bold move failed, and within a few weeks Hitler’s tanks were stuck in the snow. In 1945, after months of re-supply, the Allied armies pushed back the German forces and invaded Germany. Soviet forces advanced across Poland and surrounded Berlin. On May 8, 1845 Hitler committed suicide, after his armies crumbled from a lack of men, equipment - and fuel.

An Empire of Oil

The War in the Pacific was fundamentally a war over resources…particularly oil.

Imperial Japan spent the 1930s constructing a Pacific empire, which they called the Greater East Asia Co-Prosperity Sphere. Japan was an emerging industrial power with one of the largest navies in the world. But its economy was dependent upon imports - mostly from the United States - of steel, aluminum, and oil.

The European powers had colonized much of the Pacific World - the French in Indochina, the British in Malaysia and Singapore, and the Dutch in Indonesia. Even the United States had gone imperial, taking over the Philippines and a number of Pacific Islands.

Japan decided it needed an empire to achieve self-sufficiency. It conquered Korea and Manchuria and invaded China. It spread its empire across the Western Pacific. But the best territories - including the oil fields of Indonesia - lay outside of its reach.

To go after them would mean war with the European colonial powers - Britain, France and the Netherlands - as well as the United States.

President Franklin D. Roosevelt, alarmed by Japan’s aggression, placed economic sanctions on Japan to counter its activities. In August 1941, he ordered all U.S. oil shipments to Japan to cease. It was a bold move, one that was designed to pressure Japan to rein in its imperial expansion.

But instead of surrendering, Japan chose to launch a surprise attack on the United States. On December 7, 1941 a Japanese fleet assaulted the U.S. naval headquarters at Pearl Harbor.

But the attack was a cover for the real offensive directed against territories in the South Pacific. Japanese armies attacked Vietnam, Malaysia, and Singapore. On March 1942, Dutch forces in colonial Indonesia surrendered, allowing Japan to occupy the Dutch oil fields.

Unrestricted Warfare

In a matter of months, Japan erected an empire covering half the Pacific Ocean. But it now faced a massive problem - while it had secured the resources it would need for economic self-sufficiency, it was now at war with the United States, a nation seven times larger with an industrial base that dwarfed that of the Japanese home islands. Related: This Crazy Idea Could Be The Future Of Power Generation

After the Battle of Midway on June 7, 1942 when a Japanese fleet was decisively defeated near Hawaii, the United States began a campaign to push back the Japanese. Much of this campaign involved “island-hopping,” using naval power to re-capture crucial island fortresses occupied by the Japanese.

But another campaign went on behind the scenes - or rather, under the waves.

From 1942 to 1945, American submarines waged an unrestricted war against Japanese shipping - particularly Japanese oil tankers.

Like the German U-boats in the North Atlantic, the Americans targeted the lifelines tying Japan to its colonial possessions scattered throughout the Pacific.

But unlike the Germans, the American campaign was hugely successful. By 1945 the Japanese economy had nearly collapsed, fuel for the Japanese navy and air force was rationed, and the Japanese merchant fleet had been reduced by nearly 2 million shipping tons.

Sapped of its former strength and crushed by the overwhelming military might of the United States, imperial Japan fought on until August 1945, when several factors - the collapse of its army in Manchuria, the entry of the Soviet Union into the Pacific War, and the atomic bombing of Hiroshima and Nagasaki - compelled its surrender.

Both Japan and Germany had embarked upon wars of conquest for similar reasons - access to resources, particularly oil.

And it was shortages of oil that had ultimately contributed to each nation’s defeat.

By Gregory Brew for Oilprice.com

More Top Reads From Oilprice.com: