Postcards are usually associated with happy images of sun-kissed families playing on beaches at the seaside.

But staff at Oxford University's Bodleian Library have used a recently-acquired collection to show how cards were sent during wartime to remind people at home of conditions on the battlefield.

Over the past 60 years, Londoner John Fraser gathered postcards from around the world. He donated them to the library last year.

Now curators at the Bodleian have sorted through thousands of postcards to produce two books, Postcards from the Trenches and Postcards from the Russian Revolution.

Each book contains about 50 postcards, with the image from the front of the card printed on the right-hand page and the writing on the back of the card on the left-hand page, together with a caption explaining the contents.

Dr Samuel Fanous, the library's head of communications and publishing, said: "Mr Fraser had the eye of a true collector and an unerring knack of knowing which cards to acquire.

"Postcards can contain a great deal of historical information and their value is now being recognised. I was struck by the images and the breadth of this collection.

"The Bodleian Library is extremely fortunate to have acquired the collection and I was privileged to be one of the first people to look through it and use it to make these books."

Historian Andrew Roberts said postcards were the equivalent of today's emails and added in his introduction to Postcards from the Trenches: "The depiction of the Great War from this fine collection of contemporary postcards ranges from the enthusiastically positive - young men marching off cheerily to the Front to do their duty - to the horrifically realistic, with piles of skulls filling a ditch-like dip in the ground that hardly rates the description of trench.

"Many of them are propaganda images intended to boost support for the war, but quite enough are honest reportage of what the conflict was truly like."

Postcards from the Russian Revolution chronicles events from the first revolution of 1905, to the Bolshevik Revolution of 1917, and the early days of the Union of Soviet Socialist Republics.

The library will publish two further volumes of postcards this autumn, one showing images of the Berlin Wall, and the other of world leaders in the 20th century.

Postcards from the Trenches and Postcards from the Russian Revolution are available from the Bodleian Shop and booskhops, priced £7.99.