As these historic photos show, the early months of the war meant residents had to quickly train as soldiers before departing for Europe and leaving their loved ones behind.
In our gallery you will also see young evacuees leaving the city and residents of Goodwood Road about to embark on an outing not realising that in two months time the country would be at war. You will also see some of the first areas to be hit by the air raids and the devastation of those bombs.
MORE RETRO PHOTOS: Portsmouth 70 years ago | The oldest places in Portsmouth | Lost Portsmouth shops
Most of the area in Portsmouth destroyed in air raids has now been rebuilt, but the memories of the devastating war still remain.
More photos from this collection can be found on our new Facebook group Portsmouth Retro – you can join here.
You can subscribe here for unlimited access to Portsmouth news online - as well as our new Puzzles section.
13. The beginning of the Second World War in Portsmouth
1940: British soldiers negotiating a barbed wire defence during a seashore invasion exercise. (Photo by Hulton Archive/Getty Images) Photo: The News archive
14. The beginning of the Second World War in Portsmouth
Portsmouth blitz, January 10, 1940 - Guildhall ablaze Photo: The News archive
15. The beginning of the Second World War in Portsmouth
The second air raid on Portsmouth, August 12, 1940, and the Harbour station is hit. Photo: The News archive
16. The beginning of the Second World War in Portsmouth
Prime Minister Neville Chamberlain's diary showing the entry for the day he declared war on Germany on September 3, 1939. Picture: Imperial War Museum/PA Wire Photo: The News archive