Author Daniela Gerson has explored the little-known survival stories of Polish Jews who fled east into Soviet-controlled territories at the outset of World War II, a journey recounted in her new book, "The Wanderers."

In September 1939, following the dual invasion of Poland by Germany from the west and the Soviet Union from the east, Jewish residents of towns like Zamość faced a grim decision. Zamość, with a Jewish population comprising over 40% of its inhabitants, was initially under Soviet control before being ceded to Germany a week later. During this brief interval, approximately two-thirds of Zamość's Jewish community opted to escape into Soviet territory with retreating Soviet troops, choosing the uncertainties of Stalin's regime over the clear threat of Nazi persecution. This exodus, undertaken by an estimated 300,000 Polish Jews, offered a significantly higher, though still perilous, chance of survival compared to remaining in Nazi-occupied areas, despite the subsequent hardships faced in Soviet labor camps and isolated settlements.

Ms. Gerson, an immigration reporter and professor of journalism at California State University, Northridge, was drawn to this often-overlooked historical chapter through personal connections. Both her own grandparents and those of her wife, immigration lawyer Talia Inlender, were among those who made the arduous journey eastward. The couple, who share a professional focus on immigration, pledged to trace their ancestors' paths before their marriage, a commitment they fulfilled a decade later, accompanied by their twin children.

The research for "The Wanderers" revealed a previously unknown detail in Ms. Inlender's family history: her grandfather Leon had a first wife and five-year-old son who did not survive after staying in Zamość. This discovery, including a photograph of the son, Kolonimus, resonated deeply with Ms. Inlender and Ms. Gerson, prompting reflections on the silence surrounding such losses.

Their initial visit to Zamość underscored the city's historical significance, with the grandparents' former homes located mere steps apart. The present-day reality of Zamość as a transit hub for refugees fleeing the conflict in Ukraine also brought a modern dimension to their historical inquiry.

Ms. Gerson's subsequent travels for the book extended over four years, taking her to Ukraine, the Siberian Arctic, and Central Asia. Through oral histories from deceased relatives, encounters with survivors in Israel, and interviews with elderly individuals in former Siberian refugee settlements, Ms. Gerson reconstructs the intertwined sagas of both sets of grandparents.

The book also delves into the post-war experiences of Ms. Gerson's paternal grandparents, who arrived in the United States in 1950 using the identities and visas of another refugee family, the Blumsteins. Further research led Ms. Gerson to locate descendants of the actual Blumstein family in Melbourne, Australia, and Israel, fostering unexpected connections.

Drawing its title, "The Wanderers," from the biblical story of the Exodus, Ms. Gerson's work highlights the shared human history of migration and displacement. The narratives in the book underscore the resilience, luck, and determination of those who endured profound uncertainty, establishing palpable connections between their experiences and the challenges faced by migrants globally today.