Remembering WWII evacuation 70 years on
It's 70 years since World War II began, and people are remembering a part of it that had a big impact on children.
When politicians were sure war was coming they wanted to keep children as safe as possible, by moving millions of them out of the UK's towns and cities.
They were packed off to live with new families in the country, often without knowing where they would end up.
It was called evacuation, and on Tuesday 2,000 of those children - who are now adults - met up to remember it.
They gathered at St Paul's Cathedral in London.
The government at the time called the idea Operation Pied Piper, and it began on 1 September 1939.
Around one-and-a-half million people left cities in the first phase, and of those 750,000 were children on their own.
By the end of the war in 1945, around 3.5m children moved from cities and towns to safer areas.
It was thought that areas in the country were less likely to come under attack or be bombed once the war started.