Although most people under 40 are astonishingly ignorant about it, a great worldwide armed conflict known as World War II took place from 1939-1945 in the European and Pacific regions. It is relevant and important to know and understand because the outcome of World War II put into place the political, economic and geographical conditions and relationships that make the world what it is today. An understanding of the ramifications of WWII is central to comprehending how today’s world came to be. People under 40—heck, even under 60—would do themselves a huge favor if they learned some history and saw how that history affected today’s world.

The 1939 war in Europe was caused mostly by the consequences of the unresolved complications and volatile conditions that persisted following the end of World War I in 1918. World War I took place from 1914 to 1918 and was a struggle for the control of Europe, primarily between the Germans on one side against the French and British (aided by America after 1917) on the other side. Germany remained particularly unstable in the years after the end of the Great War (as WWI came to be known) and in retrospect, many historians now feel that another war in Europe was inevitable.

The inevitability of another European war after 1918 became reality on Sept. 1, 1939 when Germany turned eastward and attacked Poland. Having built up its military forces in direct contravention to post-WWI treaties, Germany overwhelmed Poland in a matter of a few short weeks, using their newly-developed blitzkrieg tactics. Unlike the ponderous, static, slow-motion trench warfare that dominated World War I, Germany saw the potential of combining fast-moving armored forces with close-support air power (dive bombers and fast low-altitude bombers) to deliver a decisive, overpowering blow to their enemy’s critical targets in the very early stages of the action. (Germany’s blitzkrieg tactics were so successful that the term has now become part of the popular lexicon, meaning any quick, overwhelming action, whether in sports or business or some other endeavor.)

Following a relatively uneventful 1939-1940 winter (a time period that came to be known as the “Phony War”), Germany resumed its hostilities against Europe in the spring of 1940, turning its attention westward. German forces blasted through the “Low Countries” of the Netherlands and Belgium and swung around to invade France from a point behind its main defensive eastern border with Germany. Following World War I, France fortified its eastern border with Germany with a massive wall of concrete and armament called the Maginot Line in an effort to prevent any future invasion by Germany. But Germany attacked the Netherlands and Belgium to the north and west of Germany, through the supposedly impenetrably dense Ardennes forest and then swung into France from behind the Maginot Line. France’s expensive, foolproof defense against German aggression proved to be a worthless folly.

As German forces poured into France, the French military was disoriented, confused and demoralized. Despite having numerical superiority over Germany in planes and equipment, the French utterly failed to mount an effective defense of their homeland. Desperate and panicked, France pleaded with Britain to send men and materiél to their aid.

The British did so, in the form of the British Expeditionary Force (BEF), consisting of several hundred thousand troops along with tanks and aircraft. It was a wasted effort, as the British could not buttress the listless and disorganized French forces against the brilliantly trained, highly motivated German army. Germany’s blitzkrieg tactics decimated the allied formations, inflicting severe losses and taking great swaths of French territory.

Sometimes, what might seem to be a small decision at the time can have huge long-range consequences, with repercussions that last decades into the future, even to the point of altering the course of history. Such was the case in the battle for France in May of 1940. British Air Marshal Lord Hugh Dowding made the decision to not send any of Britain’s valuable Spitfire fighter aircraft to France for the fight against the Germans. The Spitfire was generally regarded as the best fighter plane in the world at the time (narrowly edging out Germany’s BF-109). Dowding correctly recognized that Britain would soon be in a one-on-one fight for survival against Germany and any hope Britain had of fighting off the German air force (the Luftwaffe) rested squarely on the shoulders of their small contingent of Spitfires.

As I wrote in 2008:

The British proved themselves prescient when they sent only second-line Hurricane fighters to fight against the Germans in France. In spite of vehement French protests, Air Marshal Lord Dowding (head of Britain's Fighter Command) refused to allow any of Britain's valuable front-line Spitfire fighter planes to be "wasted" in what he knew would be a losing effort in France. Better to husband them for England's solitary fight to come against the Germans after France's capitulation.

By the end of May, the German forces had cornered the remnants of the allied armies into a small, vulnerable pocket in Dunkirk, near the coast of France.  It appeared that the European war would soon be over, as the German army was poised to finish the job. Exactly what happened next is the subject of some controversy, but the lessons for military planners reverberate as clearly today as they did then, some 68 [77] years ago.

Rather than sending in their armored, tank-equipped Panzer divisions to destroy the virtually defenseless allied forces, the Germans held them back. Instead, the finishing task was given to Germany's air force, the Luftwaffe. Military historians have posited that perhaps Germany's armored Panzer divisions were stretched too thin and had outrun their supply lines, and thus needed time for rest and recuperation. Another popular theory has it that the head of the Luftwaffe—Hermann Göring—was envious of the glory that his Army counterparts were getting from their numerous overwhelming victories, and he wanted to prove that his air force was worthy of similar accolades.

But regardless of the reason, the German air force was given the responsibility, and it failed. That decision remains one of the greatest military blunders of all time. The Luftwaffe flew sortie after sortie, attacking the Allied armies, but couldn't finish the job. Instead, the British organized an amazing sea-borne rescue effort and sent hundreds of ships and boats of all kinds across the Channel to rescue the beleaguered soldiers. Everything from Royal Navy transport ships to private fishing boats participated in the effort. The RAF flew cover and fought off the German air attacks. Although their losses were high and virtually all their equipment was left on the beaches of Dunkirk, almost 400,000 Allied soldiers were rescued, and survived to fight another day.

The Spitfires were the missing weapon in the Fall of France. If the British had sent Spitfires to France and wasted those invaluable, irreplaceable front-line fighter planes and pilots in the weeks prior to Dunkirk in a hopelessly futile effort to save France from the German onslaught, then surely the German Luftwaffe would have succeeded in destroying the Allied armies on the beaches of Dunkirk. Absent the Spitfire, there were no British fighter planes that could defeat the BF-109 in head-to-head combat. British Hawker Hurricane was less than equal to the 109 while the Bolton Paul Defiant was completely outclassed. In the likely event of significant Spitfire losses in the battle for France (even if just mostly from normal high-stress military service attrition and accidents), the Germans would have ruled the skies over Dunkirk and their bombers—unhindered by numerically-significant Spitfire opposition—would have exacted a decisive, fatal toll on both the trapped Allied soldiers on the beach and the beleaguered British ships and boats that were trying to help.

But that was not the case. There were enough (barely enough!) Spitfires to keep the German air force at bay in the skies over Dunkirk. Lord Dowding’s decision to withhold Britain’s priceless Spitfires from the losing, pointless exercise in France was unquestionably one of the most important, consequential decisions in military history. Few history books even mention it and neither does the otherwise-excellent current movie Dunkirk, but the “no Spitfires sent to France” decision ranks as one of the very most important military judgments of all time.

A clear indication of the Spitfire’s unmatched excellence came from an unlikely source, none other than General Adolf Galland, high-ranking German ace, who became head of all of Germany’s fighter forces later in the war. When asked by Hermann Göring (Reichsmarschall of the Luftwaffe) what he needed to be more successful in battle, Galland famously replied, “I should like a staffel [squadron] of Spitfires for my gruppe!”

At the very end of the movie Dunkirk, there is a dedication screen that reads, “Dedicated to all the individuals whose lives have been impacted by the events at Dunkirk.” It’s an intentionally subtle and brilliant statement by director Christopher Nolan, since everyone in the world since 1940 has been “impacted” by the events that took place there. Had the Germans won the war in Europe—and they were within a hairsbreadth of doing that at Dunkirk—the world would be a drastically different place today. Everyone’s lives would have been impacted. But Britain’s heroic Royal Air Force—led by those courageous pilots flying their Spitfires—didn’t let that happen.