Final answer:
On September 3, 1939, the outbreak of World War II began with declarations of war by France and the UK against Germany, significantly affecting the lives of Jewish families like the Weissmanns through increased persecution and danger.
Step-by-step explanation:
The historic event that occurred on September 3, 1939, was the outbreak of World War II when France and the United Kingdom declared war on Germany following its invasion of Poland. For the Weissmanns, a hypothetical Jewish family, this would have had an immediate and profound impact on their lives.
This era marked a dark period for Jews in Europe, with events like Kristallnacht (the Night of Broken Glass) in 1938, where coordinated attacks on Jewish people and properties took a devastating toll on Jewish communities. The United States' response to the refugee crisis and later actions, or lack thereof, regarding Jewish persecution in Europe during the 1930s and 1940s.