Ms. Orbuch was born Sarah Shainwald in what was then the eastern Polish town of Luboml. She was 16 when German forces took over the area in 1941 and began killing Jews. Her family fled to nearby forests and hid there for the winter.
By spring, they joined a group of Soviet soldiers and civilians who targeted Nazi troops by blowing up trains, ambushing convoys and sniping at outposts.
The group was reluctant to take in a Jewish family with no military skills, but the leaders were persuaded by Ms. Orbuch’s uncle, who had been a scout in the Polish army and knew the region.
The group thought her original name sounded too Jewish, so she was renamed Sonia.
She had no medical training, but Sonia learned to tend to the wounded. She kept watch and went on raids. She always carried two grenades — one for the Nazis and one for herself. She did not want to be taken alive.
“Suddenly, I was not afraid of bombs — me, a girl who had been afraid of a fly,” she said later.
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After the war, she married Isaak Orbuch and they moved to the United States. Her husband died in 1998.
Later in life, Ms. Orbuch became an author and lecturer. In 2009, she wrote her autobiography, “Here, There Are No Sarahs,” and helped found the Jewish Partisan Educational Foundation, a San Francisco-based organization that honors the memory of the 20,000 to 30,000 Jews who fought in resistance groups in World War II.
In addition to her son of San Anselmo, Calif., survivors include a daughter, Bella Whelan of Mill Valley, Calif.; and a granddaughter.
“Was it possible for everybody to fight and get out to the forest and survive? No, it wasn’t,” Ms. Orbuch said, according to the Jewish Partisan Educational Foundation. “My brother did not survive, my uncle did not survive. Many other brothers and uncles could not survive. But every person in the ghetto fought in their own way.”
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