The Dutch resistance fighter who gunned down Nazi collaborators in the streets of The Hague while maintaining the cover of a respected neurologist has been posthumously honored as one of the most daring underground operatives of the Second World War, according to historical records released on the anniversary of his death. Dr. Gerrit Willem Kastein, known to his comrades as a committed anti-fascist who traded his medical practice for a pistol, died on February 21, 1943, at the age of 32, leaping from a third-story window rather than betray his network to German interrogators.
His story, pieced together from resistance archives, court records and survivor testimony, reveals a man who moved seamlessly between the operating theater and the shadowy world of assassination, sabotage and intelligence gathering during the brutal German occupation of the Netherlands. Kastein’s transformation from physician to guerrilla fighter began within days of the Dutch capitulation on May 15, 1940, when he attended a secret meeting of Communist Party members in The Hague to plan underground activities.
Born on June 25, 1910, in the town of Zutphen, Kastein displayed an early seriousness of purpose that set him apart from his peers. He excelled in his studies and chose medicine as his life’s calling, beginning his training at the University of Groningen before continuing his education at universities in Germany and Leiden. He graduated as a neurologist in 1937, but his time in Germany had already opened his eyes to the gathering storm of fascism.
It was in Germany that Kastein met Elizabeth Zaka, a German woman who would become his wife and the mother of his two children. Their marriage and family life stood in stark contrast to the dangerous political path he was already walking. Even before the war, Kastein’s convictions had drawn him into public life, first as a member of a socialist party and later as a member of the Communist Party of the Netherlands.
He wrote articles for the party’s journal and delivered lectures warning of the dangers of fascism, campaigning actively against racism and intolerance. But Kastein was not content to fight only with words. He helped smuggle communists out of Nazi Germany and, when the Spanish Civil War erupted in 1936, he volunteered with a medical team to support the Republican side against the forces of General Francisco Franco.
In Spain, Kastein worked among the wounded, witnessing firsthand the brutality of fascist warfare. The stories of courage and cruelty he brought back only deepened his hatred of the ideology that was spreading across Europe. In 1938, he published a book condemning racism and warning about the consequences of political indifference, a work that would prove tragically prophetic.
When Nazi Germany invaded Poland on September 1, 1939, the world plunged into war. Eight months later, on May 10, 1940, German forces attacked the neutral Netherlands, with bombers striking military airfields and barracks around The Hague. Adolf Hitler justified the invasion with a lie, claiming that England and France had been planning to attack Germany through Dutch and Belgian territory.
German paratroopers descended on key tactical points, assisting the advance of ground troops across the country. Rotterdam, the vital port city, became a central target. As German troops pushed closer, the Dutch government attempted to negotiate, but the Germans demanded total surrender.
On May 14, 1940, German bombers unleashed a devastating air raid on Rotterdam’s city center, setting huge sections of the city ablaze and killing hundreds of civilians.
Thick smoke rose for miles, and the destruction shocked the nation. Under threat that other cities like Utrecht and Amsterdam would suffer the same fate, Dutch Commander-in-Chief General Henri Winkelman decided to capitulate. The following day, the Netherlands signed a surrender agreement.
Queen Wilhelmina and the Dutch government had fled to London days earlier to continue the fight from exile.
Only the province of Zeeland held out a little longer before it too was overrun. With the surrender complete, the Netherlands fell under German military occupation. Daily life changed almost overnight.
German soldiers patrolled the streets, strict curfews were imposed, and all public gatherings were controlled. The occupation authorities targeted Jewish citizens, political opponents and anyone suspected of resisting Nazi rule.
Many Dutch people felt a deep sense of humiliation and disbelief that their neutral country had been overpowered so quickly. Some hoped the war would soon be over, but others began to think about how they might resist. In this atmosphere of shock and fear, Kastein felt more certain than ever that he could not remain passive.
The sudden collapse of Dutch defenses and the brutal bombing of Rotterdam convinced him that the Nazis would stop at nothing to break the country’s spirit. For a man already committed to fighting fascism, the surrender was not just a military defeat but a moral challenge. While many around him tried to adapt or hoped life would return to normal, Kastein saw clearly that occupation would only allow the Nazis to grow stronger.
Just days after the capitulation, on May 17, 1940, he attended a secret meeting of Communist Party members in The Hague to discuss how they could reorganize underground activities. He understood that with the queen and government in exile, there was no legitimate Dutch authority left to protect freedom inside the country. From that moment on, Kastein believed it was up to ordinary citizens to resist in whatever ways they could.
The fall of the Netherlands transformed him from a respected neurologist into a determined resistance leader willing to risk everything to oppose the forces that had turned his homeland into an occupied territory. The first attempt by Nazi security authorities to arrest him came on September 2, 1941, but Kastein was warned in time and went into hiding, continuing his resistance activities from the shadows.
In 1942, Kastein worked with a resistance group known as CS6, named after the address at Corellistraat 6 in Amsterdam, where several resistance members lived and often met. The group specialized in gathering military intelligence and planning assassinations of key Dutch collaborators with the Nazi regime. Kastein also worked closely with non-communist resistance groups, building bridges across political divides in the fight against a common enemy.
He intended to have photographs of German defenses along the Dutch coast delivered to the Dutch government in London through such resistance groups. However, the courier turned out to be a German double agent, Anton van der Waals, who slipped the film roll not to the government in exile but directly into German hands. The betrayal would have deadly consequences for the resistance network.
By the end of 1942, Nazi leaders were preparing to create a Dutch Nazi administration to support Germany’s Eastern Front campaigns. The Germans believed that by installing loyal Dutch officials and terrorizing the local population, they could suppress any rebellion in the occupied Netherlands. The CS6 group decided that visible collaboration with Nazi Germany had to be punished to warn others and damage German plans.
On February 5, 1943, they ambushed General Hendrik Seyffardt, a retired Dutch officer who had agreed to serve the Germans. Seyffardt had served as chief of staff of the Dutch army before the war and retired in 1934. He came out of retirement during the occupation and served as a willing collaborator and figurehead for the Volunteer Legion Netherlands, a unit of the Waffen SS created by Dutch citizens to fight on the Eastern Front.
After receiving approval from the Dutch government in exile, the attack was carried out on the evening of February 5, 1943. When Seyffardt answered a knock at his front door in The Hague, he was shot twice by student Jan Verleun, who had accompanied Kastein on the mission. Seyffardt died in hospital the following day.
A few days later, another attack prepared by Kastein and CS6 members targeted Hermanus Reydon, a member of the Dutch National Socialist Movement and a journalist turned Nazi collaborator. Reydon was seriously wounded and died of his wounds in August 1943. His wife, Wilhelmina, died during the attack.
These attacks outraged the Germans, who launched a campaign of reprisal killings and terror. Nazi death squads and Dutch collaborators carried out executions of prominent civilians, former soldiers, doctors and priests accused of sympathizing with the resistance. Instead of destroying morale, these brutal acts spread more bitterness and made the occupation even more hated.
But the Germans succeeded in one thing: they captured Kastein. On February 19, 1943, he was supposed to meet with a fellow communist resistance fighter in Delft, near The Hague. They were to discuss a plan to simultaneously set fire to all employment offices in the Netherlands to complicate the deportation of Dutch men for forced labor in Nazi Germany.
However, German security services had caught the resistance fighter previously, and during a search, they found a note of the meeting in his notebook. Precisely on time, Kastein entered the cafe and was immediately seized by the Germans and taken to a car parked outside with false license plates. An agent from the SD, the intelligence agency of the Nazi party, was waiting in the car.
Once inside, a struggle ensued, during which Kastein managed to pull a pistol from his jacket pocket and fire, seriously wounding the German agent. When the car drove away, a small pool of blood remained on the street. During a search, the SD found a notebook containing a written record of a meeting with communist resistance fighter Lucas Boor.
Later that day, Kastein agreed to cooperate in attending the meeting. The meeting was held at a coffee house in the park. There, SD officer Johannes Hoffmann got out and walked to the coffee shop, which was about 10 meters off the road.
Kastein, whose hands were cuffed, managed to retrieve a pistol and shot another SD officer in the leg.
He then jumped out and ran away, but he was quickly overtaken. He was placed back in the car, and as it drove away, four armed men burst out of the cafe. The car drove on, and when Kastein was ordered to get out, he managed to pull another pistol and shot himself in the chest, but the bullet ricocheted.
After this struggle, Kastein was taken for interrogation. This was the moment when he made his final decision and decided to sacrifice his life before revealing any resistance secrets to the Nazis. On February 21, 1943, while being interrogated by the German security service in an interrogation room, left alone for a moment, the 32-year-old Kastein jumped, still handcuffed and attached to the chair, from a third-story window.
On landing, he fractured his skull and died a few hours later. His death was a devastating blow to the Dutch resistance, but his legacy would endure. Kastein is still remembered as one of the greatest heroes of the Dutch resistance during the Second World War, a man who gave his life rather than betray his comrades.
His story is a testament to the courage of ordinary people who chose to resist tyranny when their country fell under occupation. From his early days as a medical student in Germany, where he first witnessed the rise of fascism, to his final act of defiance in a German interrogation room, Kastein’s life was defined by a refusal to remain silent in the face of evil.
Historians note that Kastein’s contributions to the resistance went beyond the assassinations he carried out or helped plan. His work in gathering intelligence, his efforts to build bridges between communist and non-communist resistance groups, and his willingness to sacrifice everything for the cause made him a central figure in the Dutch underground.
The CS6 group, with which Kastein worked closely, was responsible for some of the most audacious acts of resistance during the occupation. The assassinations of Seyffardt and Reydon sent shockwaves through the Nazi administration and demonstrated that Dutch collaborators would not go unpunished. The reprisals that followed were brutal, but they also served to harden Dutch resolve against the occupiers.
Kastein’s wife, Elizabeth, and their two children survived the war, though details of their later lives remain scarce. The family paid a heavy price for Kastein’s resistance activities, as did countless other Dutch families who lost loved ones to Nazi terror. The occupation of the Netherlands lasted until May 1945, when German forces surrendered to Allied troops.
By the time the war ended, more than 100,000 Dutch Jews had been deported to death camps, and tens of thousands of Dutch citizens had been killed in reprisals, forced labor or combat. The resistance, though small in number, played a crucial role in undermining the Nazi occupation and keeping hope alive for a liberated Netherlands.
Kastein’s name is inscribed on memorials across the Netherlands, and his story is taught in Dutch schools as an example of moral courage. Historians continue to study his life and the broader resistance movement, seeking to understand what motivated ordinary people to risk everything for freedom.
The Dutch government in exile, which had approved the assassination of Seyffardt, recognized the sacrifices made by resistance fighters like Kastein. After the war, many resistance members were honored with medals and public tributes, though Kastein himself did not live to see the liberation of his country.
His decision to jump from the interrogation room window rather than reveal secrets under torture has been described by historians as an act of extraordinary bravery. Even in his final moments, Kastein remained committed to protecting his comrades and the cause for which he had fought.
The story of Dr. Gerrit Willem Kastein serves as a reminder that heroism often comes in unexpected forms. A neurologist by training, he could have chosen to focus on his medical career and his family, waiting out the war in relative safety.
Instead, he chose to fight, knowing the risks and ultimately paying the ultimate price.
His legacy lives on in the Netherlands and beyond, a symbol of resistance against tyranny and a testament to the power of individual conviction. As the world marks the anniversaries of the Second World War, Kastein’s story continues to inspire those who believe that even in the darkest times, one person can make a difference.
The World History Channel, which produced the documentary on Kastein’s life, noted that his story is one of many from the Dutch resistance that deserve greater recognition. The channel urged viewers to remember the sacrifices made by ordinary people during the war and to reflect on the lessons that history teaches.
Kastein’s life and death raise profound questions about morality, duty and sacrifice. Was he justified in taking the lives of collaborators? Could he have done more by staying alive and continuing the fight?
These are questions that historians and ethicists continue to debate, but what is undeniable is the impact he had on the resistance movement and the inspiration he provided to others.
In the end, Kastein’s story is one of a man who refused to be a bystander. When his country fell under Nazi occupation, he did not retreat into the safety of his profession or his family life. Instead, he stepped forward, accepting the dangers and ultimately making the ultimate sacrifice.
His name may not be as well-known as some other resistance figures, but his contribution to the fight against fascism is no less significant.
As the Netherlands and the world remember the victims and heroes of the Second World War, Dr. Gerrit Willem Kastein stands as a powerful example of what one person can do when they choose to act. His story is a reminder that freedom is not free and that it must be defended, sometimes at the greatest cost.