I saw this earlier today on FamilySearch – World War II Facts, Turning Points, Battles, and More: https://www.familysearch.org/blog/en/world-war-2-facts/.
World War II happened on a global scale. It was so big and complex that it can be difficult to think about it in terms of actual people—mothers and fathers, brothers and sisters, aunts and uncles—families whose lives and relationships were never the same again.
It’s likely that someone you are related to experienced a major upheaval in his or her life on account of the war. FamilySearch.org is a place to learn about these people, your ancestors of the 20th century. You can start by finding historical records that reveal where they were and what they were doing.