Irena Sendler (1910-2008) was a Polish social worker and human rights advocate that saved over 2,500 children from Warsaw ghettos until the Nazi regime ended in 1945. During the Nazi regime, she worked for an underground anti-nazism organization called Zegota that helped fund more of her missions. She also became head of the Department of Care of Jewish Children in Zegota in 1943. However in the same year, she was arrested when a laundry owner exposed her work to the Gestapo. She was then tortured so that she can reveal any information about the children that she rescued, but she told them nothing. Because of this, she was going to be executed in 1944, but Zegota bribed the Gestapo to free her. Over two decades later, she was recognized for her bravery and was given the Rightoues Among Nations Medal in 1965.
How she smuggled the children: Irena Sendler used her social worker status to get a permit to go into the Warsaw ghettos to "check the sanitation inside" and start her rescue missions. If they were small children, she placed them in boxes, briefcases, toolboxes and coffins. Bigger children escaped through a sewer systems. After rescuing the children, she then gives them new identites and finds them safe houses. Due to her being a social worker, she also had an easier time giving the children over to orphanges with their false indentites. To keep track of each child, she wrote each name and their records on tiny sheets of paper and placed them in glass jars. The jars were never exposed to the nazis because before her arrest, she gave them to her trusted friend Janina Grabowska.
Sources:
-Ted-Ed, United States Holocaust Memorial Museum,Yad Vashem
-https://www.youtube.com/watch?v=pTJY6IBgVhY