Though she shared her classmates' pride in the IDF, she didn't have the same connection to Israel as many of them did: Ms Külow and her mother had converted to Judaism only a year earlier. "I had never been to Israel, had no relatives there, I had no link to Israel except for being Jewish," she says.
But "Germany is my home, where I grew up, where my family and friends live, and that is what I want to defend."
Today, Ms Külow - who wears her gold Star of David pendant next to the gold heart from her fiancée - is not only a Bundeswehr captain. She is also co-chair of the Bund Jüdischer Soldaten, a 10-year-old organisation dedicated to teaching members of Germany's armed forces about the history of Jews, as well as to advocating for Jews in today's Bundeswehr. No one knows exact numbers, but insiders guess there are some 200 Jews in a military of about 200,000.
Ms Külow was born in former East Germany. Her parents divorced when she was one. Years later, her mother - who had long been on a path to Judaism - asked her if she wanted to learn an extra language. "How about Hebrew? And learn about the Jewish religion?"
"Of course I said yes," laughs Ms Külow, her eyes twinkling. "What kid doesn't want to do something extra?"
She converted at 14, together with her mother. "I was nervous as hell," she said, adding that she was afraid she would not make it. But she answered the rabbis' questions and even read a text in Hebrew. "Do I have to translate it?" she asked. "No, just read it," they told her. She passed.
That classroom encounter, just a year later, was the start of a difficult period for Ms Külow.
Her classmates "were teasing me in a bad way". Even the school principal tried to talk her out of it. Ms Külow answered: "I want to help people. I know it sounds strange: a soldier is connected with war. But I see it as helping people who don't live in a peaceful environment.
"What helped me at the time were my friends," she recalls. "They said, 'You will go your own way, don't listen to them.' This lifted me. In the end, I made the decision to go into the army."
Ms Külow joined right after high school. She was inducted in the same military buildings in Muenster where her father's father - captured shortly after enlisting in the Navy during the Second World War - was held in a British military prison.
Following basic training, she earned bachelor's and master's degrees in political science from the Helmut-Schmidt-University of the Bundeswehr in Hamburg. She wrote her bachelor's thesis on US-Israel relations, and her master's thesis on the perception of the "Arab Spring" in Israeli media. She also learned Hebrew at an ulpan at Ben Gurion University in Beer Sheva.
Ms Külow found out about the Jewish soldiers group from her maternal grandmother. "She used to cut out newspaper articles and send them to me."
Eventually, they invited her to an event commemorating the more than 100,000 Jews who fought for Germany in the First World War - about a fifth of the German Jewish population at the time. Hitler later blamed Germany's defeat on Jewish soldiers.
Ms Külow met members of the Jewish association at the commemoration, and eventually became involved in an historical research project with them. Last April, she was elected to the board.
The association used to be more focused on the past, Ms Külow says. "Now, we're looking at what can we do for Jewish soldiers today and on making connections with other armies."
The association is growing bigger and younger, but - despite a website and an active Facebook group with articles about current activities - outreach is difficult because it is against the law to ask soldiers to reveal their religion, Ms Külow says. Also, she says, "some Jews don't want people to know they are Jewish. So they wouldn't join."
In part, Ms Külow sees her role as that of an educator. "Many Germans have no idea about Jewish people, and many Jews have no idea about the Bundeswehr," she said. "They still have the impression that it is the Wehrmacht."
When Jews ask if there is antisemitism in the German military, she reminds them that anyone who shows any signs of sympathising with Nazi ideas, who is racist or antisemitic, "has to leave the army immediately. You take off your jacket and go. That was very impressive to me," and it impresses them, she said.
But just as remarkable was how her fellow soldiers reacted when she showed up for breakfast, lunch and dinner with matzot during Passover.
"What does our first lieutenant have there? What is she eating there?" her colleagues asked.
"I explained about Pesach, about the Exodus from Egypt, and I explained about the matzot. They were pleased to know more and very open. I never had any bad experiences."
She would like fellow soldiers to lose their fear of being openly Jewish. "Don't be afraid to tell your superior you want to observe Yom Kippur," Ms Külow said.
Today, there is a new attitude at the Jewish high school. They have even asked her to give a presentation there. Instead of questioning her decision, today teachers "tell me to 'be safe'. They care about me."
