The German Invasion
In 1936, Koos joined the Red Cross in Maastricht, the Netherlands. The hospital in Roermond had turned her down for being too young, but she was determined to become a nurse and joined the Red Cross education program. Maastricht’s location near the border made it likely to be on the front line if war broke out.

In 1939 Koos took the Red Cross oath and from that moment on she could be send to war zones. Her mother was really worried about her profession and her father, a very practical man, advised her to keep a diary, in case anything would happen to her. Koos followed his advice, and these diaries would later be published, giving us insight into her experiences.

Koos had become an au-pair in Liège, Belgium, where she learned French and taught Dutch to the children of the family she lived with. She also became friends with Stina Hülpers, a Swedish girl staying in the city.

On May 10, 1940 the Germans invaded Belgium. The family she stayed with asked Koos to flee with them to France, where it’s safe. But Koos thought of home and the people who needed her. She decides to go back to the Red Cross at home and help the Dutch. She called with a Dutch lieutenant, who was stationed at Koos’s parents’ house. He told her that the Germans will be at the river Maas in two hours and that he’s going to blow up the roads. He hurried her to come get her parents. Koos could only go back home by bicycle, which was 30 kilometres and usually takes two hours.

She set off at night, wearing a compass around her neck. She saw Belgian soldiers preparing for battle and slowly realized the full reality of war. At a small village near the river Maas, 16 kilometres from home, she was stopped by a soldier: the road was cut off. At the same time, German aircraft flew overhead, dropping bombs, while Belgian troops fired back. Bombs fell around her, bridges were in danger of being destroyed, and Maastricht might be completely cut off. Fear and urgency propelled her forward, even as she felt powerless.

Koos cycled as fast as she could to a nearby bridge, while the bombing intensified. People are running the streets, some injured, there’s total panic, the air alarm sounded continuously. She sees the sun coming up in a blue sky filled with German bombers. Koos’s head spun, she didn’t know which route to take. She’s worried about her friends and families and her country. With her compass she navigated in the direction of Brussels to see if she can enter the Netherlands from there.

Koos avoids the big roads and goes through the hills and fields. She cycles and cycles, not knowing where she’ll spend the night or how to get some food. And then she got a flat tire and couldn’t continue. She goes to a nearby farm. One of the boys fixes her bicycle and they offer her food and a place to spend the night. The whole family gathers around the radio to hear the latest news. They are warned not to go on the streets. The radio played the Belgian anthem. They can also get the Dutch news, where they play the Dutch anthem. Koos felt overwhelmed. The lady of the house tells her she can’t continue her journey as the Germans made their way close by. The news on the radio gets worse and worse. And then they hear the bombers above the farm house, the whole family flees into the basement, while the bombs rain down on them. Luckily, the farmers has food in storage, like meat and bread, biscuits. Their son was going to marry in two days and they prepared all the food and stored it in the basement. So ,they don’t have to worry about food. There’s no electricity anymore. Koos prepares the basements, so they can house 25 people. More people from nearby farms come to the basement. All the houses and buildings are shattered and are burning. Meanwhile, in between the bombing they need to keep the farm going, like milking the cows and taking care of the animals and the stables. They need to be on the lookout for bombs.

They help wounded Belgian soldiers, who were taken off guard by the German invasion. The Belgian soldiers retreat, while they stay behind on the farm, in the hands of the enemy. Endless bombing continues. Waiting for the enemy to arrive. Koos is the only one that speaks German, so she needs to confront the Germans. Germans point a gun at her. The German soldier is surprised the speaks Dutch. German soldier explains to her they don’t care about Belgium, they want to take England. The German soldiers kept coming. She gives them some cigarettes. And they asked her for directions.

Eventually, she resumed her journey toward Maastricht, navigating through a landscape filled with death, destruction, and the remnants of plundering German troops. Despite warnings from German soldiers not to proceed, her determination and anger for her occupied country drove her onward. On her way she saw death Belgian soldiers laying around. German soldiers singing and laughing. Plundering, chaos. People are devastated. Finally, after days she arrived safely in the Netherlands. She was home.

Searching for a friend
After returning home, Koos was ordered by the Red Cross to build a field hospital in a newly constructed monastery. Within a week, she had it operational, caring for severely wounded Allied POWs — Belgians, French, Moroccans, and Algerians who had fought against the German invasion. By July 1940, wounded British POWs also arrived; those with minor injuries were quickly sent to Germany, while severely wounded prisoners were sent back to Belgium and France. By September, the field hospital closed after all POWs had been transferred.

Koos then learned that her friend Stina had gone missing in France. Part of Stina’s family had been imprisoned, and a young child killed. Concerned for her friend’s safety, Koos used her Red Cross credentials to obtain permission to travel to France, despite wartime restrictions. She went by train – which carried German troops – hitchhiking and walking up to 25 kilometres at a time.

During the search, she fell seriously ill with pleurisy, pneumonia, and tuberculosis. In the French hospital, she met young Dutch lorry drivers forced by the Germans to transport goods. Secretly, they brought her food and medicine and informed her parents of her condition. Her father was eventually granted permission by German authorities to visit her in the hospital.

Even while gravely ill, Koos shared with her father her suspicion that Stina might lie in one of the graves she had investigated. When a grave was opened, it contained a German soldier instead. The Germans were grateful for her careful handling and allowed her to return home to Maastricht by Red Cross ambulance. There, Koos spent months recovering and began keeping a diary, documenting her experiences for the first time.

By July 1944, Koos received a health declaration and returned to work for the Red Cross. She was assigned to a field hospital in Sint-Oedenrode, caring for elderly and disabled patients relocated by the Germans from areas being prepared for the Atlantic Wall, a defensive fortification. This assignment was expected to be less stressful, giving her time to regain strength. Meanwhile, the Allied forces were steadily advancing through France and Belgium, preparing to liberate more of the Netherlands.

Hell’s Highway
In September 1944, Operation Market Garden began. The operation aimed to capture key bridges in the Netherlands: Operation Market focused on airborne landings, while Operation Garden aimed to clear the way for the British Guards Armoured Division. The road between Son and Grave, with Sint Oedenrode at its center, became a lifeline for the advancing troops — but also a deadly battleground. The road was later nicknamed “Hell’s Highway” because of the constant attacks, shelling, and chaos along its route.

The Red Cross field hospital in Sint-Oedenrode became a refuge for wounded Allied and German soldiers. Inside, German medical staff and Red Cross staff were quartered, and Koos, along with her friend Willy, were the only Red Cross nurses. Their duty was clear: to care for all wounded, regardless of nationality. But Koos could not ignore the tension inside herself. The German medical staff had once been her country’s oppressors — were they now friends, or her foe?

The fighting outside the hospital was relentless. RAF planes dropped bombs nearby, while artillery shells shook the ground and American and German soldiers battled just beyond the walls. Yet inside, the hospital existed as a neutral space. Every medical professional, regardless of allegiance, focused solely on saving lives. Koos moved from bed to bed, tending to soldiers she had once viewed as enemies, keeping her emotions in check while the world outside burned.

Working closely with the German medics brought a mix of fear, suspicion, and unexpected respect. They were once the enemy occupying her homeland, yet now they followed the same humanitarian principles that guided Koos. She wrestled with conflicting emotions: anger at the German army’s actions, but admiration for their dedication to saving the wounded. In the hospital, friend and foe blurred, and morality was measured by care, not nationality.

Eventually, the Americans liberated the area. The German medical staff became prisoners of war, but under the Geneva Convention, they were allowed to continue their work. Koos witnessed a strange reversal: her former oppressors were now POWs, yet inside the hospital, the work continued unchanged. The wounded were treated, and the principle of neutrality endured.

Later, the German staff and patients were transferred to the Sint Joseph Hospital in Eindhoven, which had been empty. A section of the second floor was dedicated to wounded POWs. Koos and Willy were allowed to return home to Maastricht, but the German doctor pleaded for their help, explaining he lacked enough staff. Despite concerns that the Dutch might see them as pro-German, Koos and Willy agreed. They travelled with the German staff to a British POW camp, caring for wounded German soldiers. The British army provided housing, rations, chocolates, and cigarettes, allowing the nurses to continue their work safely.

When new German medical personnel arrived, Koos and Willy left and continued their service at an evacuation camp in Moll, Belgium, staying there until the entire Netherlands was liberated. Through it all, Koos experienced the complexity of war firsthand: enemies could become colleagues, neutrality could save lives, and moral courage meant caring for all, even those who had once caused so much suffering.

After the war
Back in Maastricht, Koos joined the United Nations Relief and Rehabilitation Administration (UNRRA) in 1945, helping refugees across Europe. Her wartime experiences — balancing duty, danger, and moral responsibility — shaped her lifelong commitment to humanitarian work.
Koos’s story is a powerful example of courage, integrity, and the difficult moral choices faced in war. She navigated the thin line between friend and foe, always guided by the principle of impartial care.