Their haircuts, primitive spectacles, pensive faces - and above all their gas masks - mark them out as the children of an earlier, more terribly threatened generation. With luggage labels round necks and cardboard suitcases in hand, they were packed off to railway stations in their millions.

Many knew they would not see their parents again for years. For they were the evacuees - the generation sent to the countryside to escape the Nazi bombing of British cities during the second world war.

The exodus is recalled in a new book of official photographs, many of which have not been seen since they appeared in wartime publications more than 60 years ago.

So high was the calibre of photographers recruited by the Ministry of Information that images intended as morale-raising propaganda have survived in the Imperial War Museum as richly informative social documents.

The evacuees were photographed arriving at Kingsbridge, Devon, from Bristol. Two of them wear spectacles which pre-date the foundation of the National Health Service by seven years.

Mothers cut the boys' hair by placing pudding-basins on their heads. The girls' hair was roughly scissored. Gas masks were standard issue to everyone in Britain, including babies.

The book's author, Emma Crocker, the curator of the war museum photographic archive, recalls that a prominent scientific expert on gas warfare, Professor J B S Haldane, argued against mass evacuation. His thesis that "the concentration or dispersal of people would have no bearing on the effectiveness of bombs" was officially rejected.

Ms Crocker says: "The experiences of children during the second world war had a huge impact on their lives and it is clear that they involved much more than being herded passively on to trains to the country. Despite some bad times, the evacuees learnt a huge amount about Britain and how the other half lived."

Another photo, titled Sniffer, taken in Poplar, east London, shows a dog called Rip which was one of eight to win the Dickin medal for bravery and skill for his work in detecting people still alive under the rubble of bombed houses. His handler, a middle-aged civilian air raid warden, is urgently beckoning rescuers to dig where the dog is sniffing.

The Home Front in Photographs (Sutton Publishing, £19.99)