The Siege of Bilbao, 1937. Basque Culture Systematically Erased. Hitler Helps Spain in a Preview of WWII Atrocities and Experiments.

 The fall of Vizcaya’s capital was both a tactical defeat and the moment the spine of Basque resistance snapped. With it went the last coordinated defense of autonomy in the north. From that point forward, there would be no organized Basque military stand, no political bargaining power, and no seat at the table in the war that continued to rage across Spain.
What followed was more than occupation; it was a deliberate and calculated dismantling of Basque nationalism. Schools were purged. Language forbidden. Symbols outlawed. Nationalist Military leaders didn’t just take territory, they moved to erase the very idea of a separate Basque identity.
That loss in Vizcaya marked more than the end of a campaign. It triggered a generational suppression that would outlast the war itself: etched into law, enforced by decree, and remembered in silence.

Bilbao. March 31 - une 19, 1937.
Spanish Nationalist Forces: ~ 50,000 Spanish, Italian, and Moroccan Troops.
Basque Republican Forces: ~ 45,000 Troops.

Additional Reading and Episode Research:

• Thomas, Hugh. The Spanish Civil War.
• Gibbs, Jack. The Spanish Civil War.
• Jackson, Gabriel. A Concise History of the Spanish Civil War.

Transcript

Thanks for tuning into this episode of History's Greatest Battles, season two, where we explore history's greatest sieges. If you know anybody that enjoys this genre of history, please share the podcast with them; and, give us a review.

Spain in 1936 was not a unified nation but a fragile collection of competing ideologies and identities, monarchists, anarchists, communists, Catholics, regional nationalists, all compressed into a republic that had only narrowly held itself together for five years. When the military uprising began in July of that year, what followed was not simply a civil war, but the testing ground for political and military doctrines that would shape the 20th century. Among those fault lines, none were more strategically vital or symbolically charged than the autonomous northern territories held by the Basques.

The Basques were a conservative, deeply religious people who had supported the Republican government not out of ideological alignment but in defense of their newly-won autonomy. They were not communists, not socialists, they were Catholic nationalists with a homeland to protect. But the war forced them into an alliance with factions they neither trusted nor respected, and ultimately left them isolated between two enemies: Franco’s centralizing dictatorship and a Republican government that viewed them as expendable.

The campaign that unfolded in the north did more than determine local control; it reshaped Spain’s internal balance of power. Its outcome dismantled Basque political independence, provided Franco with critical industrial resources, and offered a live-fire test environment for modern warfare, particularly for German air units who would later apply these lessons in Poland and across Europe. The political aftermath redrew the relationship between the Catholic Church and authoritarianism, sending a message to the rest of Europe that religion would not stand as a barrier to militarized nationalism.

The events that took place in the north were not a sideshow. They were a preview of what the world would become, military power used to crush regional identity, foreign intervention used to rehearse broader war, and religious institutions brought into alignment with authoritarian rule. The implications weren’t confined to Spain. They echoed forward, shaping the way the Second World War would be fought and how postwar Europe would be politically constructed.

As Spain edged toward full-blown civil war, one question haunted both the Republican leaders in Madrid and Franco’s insurgent generals alike: where would the Basques stand?

For years, Basque Nationalists had thrown their weight behind the reformist tide in the Republic. Yet they were a devout people, unshakably Catholic, and the Church had made its allegiance clear: it stood squarely behind Franco.

When the shooting started on July 18, 1936, Basque officers in the north moved fast. They rounded up mutinous troops and publicly pledged their loyalty to the Republic.

But Madrid had reason to worry. The Republic was shifting hard to the left, and the Basques, deeply conservative by nature, were no natural allies to a government veering toward socialism.

Franco’s camp had their own problem: the Basques had just won autonomy under the Republic. The last thing they’d submit to was a centralizing military regime.

Northern Spain was no monolith. Political unity was nowhere to be found.

In Vizcaya and Guipozcoa, Basque Nationalists held the high ground, politically and culturally.

Santander, wedged in the center, leaned toward socialism. The UGT labor union called the shots there, and its grip was firm.

Out west in Asturias, hardline communism ruled the streets. But even they answered to no one, not even the Republican government they were supposed to be fighting for.

That chaos bled straight into the battlefield. Military coordination was a disaster, rival factions ignored commands, refused cooperation, and treated orders as suggestions.

Franco’s rebellion in the north was led from a junta in Burgos, with General Emilio Mola at the helm. His forces advanced like a tide, pushing from the Portuguese border all the way to Catalonia in the northeast.

Though the Basque heartlands along the coast weren’t taken, they were cut off, severed from the Republican center in Madrid and left to stand alone.

On September 4, the Nationalists took Irún, a key border town. With that, the Basque provinces were encircled, boxed in with no way out.

The north then fell quiet. Franco had his eyes on Madrid, and for a time, the Basques were spared the hammer blow.

When Mola launched his offensive into Basque soil on March 31, 1937, the Basques weren’t just hit militarily, they were politically cut adrift.

Franco’s side, still hoping the Basques could be peeled off diplomatically, sent feelers through the Vatican. Pope Pius XI ordered a letter with terms of peace to be dispatched.

But the Republicans got their hands on the letter first, and leapt to a damning conclusion: that the Basques were trying to cut a deal behind their backs.

Their response was swift and cold. Every drop of military aid to the Basques was shut off.

Now isolated by sea and betrayed by their supposed allies, the Basques were left to fight alone, a war with no backup, no margin for error.

Bilbao wasn’t just a city, it was the industrial lifeline of northern Spain. Home to major arms plants, iron ore veins, and a crucial river port on the Nervión, it was a prize no side could ignore.

The front lines were dangerously close, only thirty miles out, stretching from Deva through Vergara to Villareal. But between them and Bilbao stood jagged, punishing terrain.

On paper, defenders had the edge in that kind of country. But the Basques lacked the essentials, armor, air power, heavy guns.

They mustered around 45,000 men. But they had just twelve tanks, a few outdated aircraft, and barely enough artillery to matter.

Franco’s 50,000 strong, backed by Italian troops, ruled the skies. The air belonged to them.

For months, the Basques had been fortifying the hills around Bilbao, hammering together a defensive perimeter they called the “Iron Ring.” By spring, it was still unfinished.

Worse, the design was flawed. Most of the fortifications sat exposed on hilltops, perfect targets for Nationalist guns and bombers.

And then came betrayal: one of the Iron Ring’s own architects switched sides, taking the entire blueprint straight to General Mola.

Add to this the constant backbiting between Basque nationalists, socialists, communists, and anarchists, and what you had was not a united front, but a fractured defense barely holding together.

Before launching his assault, Mola made his intentions clear in a chilling ultimatum: “Those not guilty of assassination and who surrender their arms will have their lives and property spared. But, if submission is not immediate, I will raze all Vizcaya to the ground, beginning with the industries of war.”

The offensive opened on March 31 with thunder from the skies. Nationalist bombers, led by Hitler’s Condor Legion, German aircraft and pilots on loan to Franco, pounded Basque positions without mercy.

Their opening strike hit the road junction at Durango, a quiet town with no defenses and no military value.

Durango had nothing to do with the battlefield. No garrison. No gun emplacements. Still, nearly 250 civilians were killed, one of history’s first experiments in terror from the air.

On the ground, the Basques fought with grit. Tank traps, barbed wire, and stubborn resistance slowed the Nationalist advance, but only briefly. Pressure mounted, and the defenders gave ground inch by inch.

Then came April 26, and Guernica. The Condor Legion returned, this time targeting the symbolic heart of Basque identity. No defenses. No military targets to speak of.

It was market day. Civilians crowded the streets. Late in the afternoon, the first wave of German bombers appeared overhead, then another.

High explosives rained down, followed by incendiaries. Buildings were blasted apart, then set ablaze. Those who ran were gunned down from the air.

The sole military target, the Mundaca River bridge, was left untouched. Instead, 1,600 civilians were killed. Nine hundred more were maimed or burned.

Word got out. Survivors told the world what had happened, and for the first time, Franco’s cause began to stink of atrocity.

The Germans blamed the Spanish. The Spanish blamed retreating Communists. Nobody took responsibility.

Years later, at Nuremberg, Hermann Göring gave the truth away: Guernica had been a test, a grotesque trial run to see how different bombs performed against a live town.

As the world gasped in horror, the Basques were still locked in a losing fight, pushed back day after day under unrelenting Nationalist fire.

They made their stands on the heights, dug in with determination, but when flanked, they pulled back, refusing to be trapped and slaughtered.

Yet the Basques hardened. The roar of bombs that once sent them scrambling became background noise. They no longer flinched at the sound.

On May 1, they got a break. A mine off Bilbao tore into the battleship España, sending it to the bottom and cracking the Nationalist blockade.

What had seemed a noose turned out to be loose. British ships began slipping through, bringing in vital supplies.

Then in mid-May, Madrid reshuffled the deck. Juan Negrín formed a new Republican cabinet, and five Basques were at the table. At last, the north began to see real support.

Heavy rains stalled the front for weeks. In Bilbao, the defenders took the pause to reorganize. Command was shifting.

General Gamir Ulibarri took the reins and sharpened the lines. Soviet aid began to filter in, not just weapons, but advisors with cold eyes and colder tactics.

General Ian Berzin arrived with Kremlin authority behind him. His presence brought more than strategy, it brought fifty-five Soviet anti-aircraft guns that arrived in early June.

Madrid tried sneaking aircraft in through France. Paris sent them back, stripped of their guns.

So they risked a bold gamble, flying them straight over enemy territory. Seven out of ten made it.

It wasn’t enough. The Condor Legion dominated the skies, and most of those planes were torn apart before they could even lift off again.

On June 3, General Mola’s plane went down. The cause? Unknown. An accident, or something darker. Franco didn’t mourn.

Some whispered of sabotage. A time bomb, perhaps. Mola had been a rival, one Franco would not miss.

General Fidel Dávila stepped in. On June 11, he unleashed hell, artillery pounded Basque positions from dusk to dawn.

That night, Nationalist troops broke through the front and reached the edge of the Iron Ring.

The guns didn’t stop. Through the darkness, more batteries rolled into place, hammering the defenses hour after hour.

On June 12, they hit the weakest spot, precisely where Goicoechea, the traitor, had told them to strike.

What followed looked like a preview of blitzkrieg: tanks rolled in right behind the barrage, so close the defenders couldn’t tell when the artillery ended and the armor began.

By sundown, the line had been shattered across nearly a kilometer. Bilbao itself was now in the crosshairs.

Bilbao’s military council vowed to make a stand, but they started evacuating civilians to the west.

Children were packed onto foreign ships, sent to safety in France, Britain, or, if their parents were Reds, the Soviet Union.

Some never reached the other shore.

Two evacuation ships were seized by Franco’s navy. The Condor Legion strafed the fleeing columns, no mercy, no restraint.

Defenders repositioned outside Bilbao, trying to regroup. The fight didn’t last.

The left flank collapsed. Retreat came so fast, the bridges over the Nervión were left intact. On June 15, Franco’s forces crossed.

Everywhere, the Basques were in retreat. The left side of the line was disintegrating.

On June 17, Bilbao was bombarded with 20,000 shells. The defenders caught even more.

June 18 was evacuation day. Civilians and equipment streamed west. The end was hours away.

That night, the order came: abandon Bilbao. When Nationalist tanks rolled in at noon on the 19th, the city was ghostly and silent.

A handful of collaborators emerged, smug, unafraid, to greet the victors.

Franco, coldly methodical, ordered only a limited troop presence inside Bilbao. He’d learned his lesson from earlier conquests.

In Málaga, Nationalist troops had looted with abandon. Franco didn’t want a repeat. Bilbao had to fall with discipline, not chaos.

The victory was absolute. Historian Hugh Thomas put it plainly: “The fall of Bilbao marked the end of Basque independence. The conquerors made every effort to extinguish Basque separatist feeling.”

Teachers were fired unless they could swear political neutrality. The Basque language was banned.

Some anarchists wanted to torch the university and St. Nicolás Church in a final act of defiance, but Minister Leizaola held the line. He forbade it.

Bilbao was battered from the shelling. But the mines, the factories, those engines of war, were left intact. Franco now owned them.

Those assets would feed his war machine for the rest of the campaign.

But the impact of Bilbao’s fall went beyond strategy, it rocked the Roman Catholic Church from within.

The Basques were the most devout Catholics in Spain.

So when a so-called Catholic movement firebombed Guernica and crushed Basque identity under its boot, many within the Church began to question who truly held the moral high ground.

Pope Pius XI declared every priest and nun slain in the war a martyr for the faith.

Meanwhile, Franco-aligned bishops doubled down, calling the Nationalist cause holy, blaming the war entirely on Communist aggression.

Basque priests who refused to follow Rome’s orders and support Franco were publicly condemned.

And then it was final.
 On August 28, 1937, the Vatican, the seat of Saint Peter, made it official: Franco’s regime was now the legitimate ruler of Spain.
 To be Catholic, from that moment on, meant to reject the Republic.

Franco’s legions pushed west without pause. By October 21, 1937, the entire northern front was his.

The fall of Vizcaya’s capital wasn’t just a tactical defeat, it was the moment the spine of Basque resistance snapped. With it went the last coordinated defense of autonomy in the north. From that point forward, there would be no organized Basque military stand, no political bargaining power, and no seat at the table in the war that continued to rage across Spain.

What followed was not a mere occupation, but a deliberate and calculated dismantling of Basque nationalism. Schools were purged. Language forbidden. Symbols outlawed. Franco didn’t just take territory, he moved to erase the very idea of a separate Basque identity.

That loss in Vizcaya marked more than the end of a campaign. It triggered a generational suppression that would outlast the war itself, etched into law, enforced by decree, and remembered in silence.

And in that silence, something deeper than a battlefield was lost.
 It was the moment faith was used to chain the faithful.
 It was the day the Church chose order over justice.
 And the night a people who had given everything were told, by both God and government, that they no longer existed.

This was not just a conquest.
 It was annihilation, signed in blood, and sanctified with a blessing.

 Thanks for listening. Let's now descend into the killing fields of the comment section On our last episode, the Siege of the Alamo, we had a few comments. I'm gonna read a few of them and then I'm going to read my reply to it.

John Hutton two five oh oh wrote A good Alamo history is by the Mesan Tibo ii. Called no Opta Para Hollywood. Most Americans can't read it because even educated Americans have problems with English. Nevermind the language is spoken and what became Texas at the time of the American's invasion. And consequent theft of Texas, Arizona, New Mexico, California, Nevada, et cetera, that Mexico found slavery incompatible with.

Democracy was a recognized factor in America's theft and is why Texas became a slave state. Said treaty was signed in European language by Europeans. What about Americans not mentioned, I repeat, not mentioned in this history. You idiots really need to read a real history. I then replied to that particular one, but that's not the reply I'm gonna read on that same thread.

Biff Markum 5 0 1 4 wrote actually the Mexican anti-slavery law did next to nothing. It did not free any slaves. It was kind of a 99 year, the lay of freedom, to which I also replied. And then John Hutton came back. I don't know if you understand that Mexicans seem aware of the theft of Mexico by the European invaders, as do Peruvians, Metis, and most mestizo in this case, most Mexicans, an archetype from Ojo DeRio and Pancho Villa.

To Jesus Malverde and the current narco Tante is the Robinhood anti-hero whose vengeance and justice is aimed at the white patron who's raped a mother or sister. . Integral is the understanding that the people El Pueblo were illegitimate. Hence the importance of civil registry of birth, marriages and deaths.

There was always a fundamental difference in occupation. The Spanish royalty were after gold and silver, the English, Fs, and trade. What became the USA? Let's use the misnomer quote. Americans had their stated Manifesto. Destiny, the very term implies a divine machination. To wit the land, hence the word steal. Holding a gun to an individual's head or to a people's head is still theft, be it Haida or Mestizo. And then in uh, brackets, he writes inappropriate because the Canadians indeed never held a gun to the Haidas head.

Hence they now have Dominique over their ancestral lands. But yeah, I'm not diplomatic. I shouldn't use intentionally incendiary language. I didn't expect anybody to actually read and address some stupid, ran to a YouTube video. You're right, probably counterproductive and I should take a good, hard look at such a poor decision.

So he was, he was replying to some of my comments that I had already replied to him with, but I'm going to sum it all up by reading my final comment to him. This is what I wrote. John, you're clearly thinking deeply about the legacy of conquest, and that's important because yes, the history of the Americas.

And the world more broadly is a history of dispossession, violence and the unequal application of power, but it's essential to approach these truths, not solely with anger, but with accuracy. Let's start with the word stolen. The United States like every great empire before it, Aztec, Inca, Spanish, French, British, Russian, and yes, even indigenous nations acquired territory through force.

This is not to excuse it. It's to recognize that conquest is not a uniquely American phenomenon, nor is it solely a white man crime. It is a holy human pattern. Every border on earth is written in blood and sealed by power. The idea that pre-colonial societies lived in peaceful, egalitarian harmony is a comforting myth that violently collapses under even the most basic historical scrutiny.

Take the Haida, whom you mentioned. My best friend since high school has a full heated great-grandmother. They are a proud and sophisticated people, warriors, traitors and builders of maritime culture with deep spiritual and territorial claims, but they were not passive victims of history. The Haida fought territorial wars with the new Chand North that some Chaon and the coastal Salish, they rated deep into the Pacific Northwest and even as far as California and the Aleutians.

The idea that quote, Canada never held a gun to the Haidas head on end quote is not historically accurate. The Haida were devastated by smallpox faced gunboat diplomacy in the 19th century, and their lands were brought under Canadian dominion without treaty. The current negotiations over land title and sovereignty are happening precisely because their land was conquered without consent, not because it wasn't taken.

Likewise, many indigenous empires in the Americas engaged in conquest. Long before Europeans arrived, the Mexico, or Aztecs, as an example, built a tributary empire through violence, extracting labor goods, and sacrificial captives from surrounding peoples, some of whom later allied with the Spanish.

Precisely because of that oppression. Again, this doesn't excuse the brutality of Spanish conquest, but it places it in the correct human context. Your point about manifest destiny is taken well, it was a doctrine that combined nationalism with theology, a belief that expansion was not just justified but ordained.

That ideology helped rationalize the displacement of Native Americans and the seizure of Mexican territory. But again, doctrines like manifest destiny are not new. Every imperial system creates its own version of divine right of historical necessity to justify its actions from the divine pharaohs of Egypt to the emperors of China, from Inca sun worship to Aztec human sacrifices.

Every power justifies its reach. What makes the American story distinct is not that it includes theft, but that it continues to wrestle often painfully and incompletely With that theft in public, no empire in history has ever built such a vast archive of self-critique. We should absolutely tell the full story of Conquered land, yes, but also of complex peoples competing ideologies, legal systems, imperfect attempts at justice, and the ever present tension between power and principle.

This story belongs to all of us, not just the victors and not just the wounded. And when we reduce that story to simple binaries, vanquished equals good, and victors equals evil. Indigenous and invader, white and brown. We strip away the nuance that actually allows us to learn from it. That's not justice, that's tribalism.

Dressed in moral language, popular virtue narrative regarding reflection on tone. Passion matters, but so does clarity and history deserves both. Thanks for listening. See you guys tomorrow.