The Imperial War Museum has reopened after a major refit and looks pretty dapper, even though it was overrun by hordes when I visited (it was still the school holidays). There’s a new and effective restaurant, inevitably, but also a new sense of spaciousness.

I am not concerned here with weapons of mass destruction, merely with the record of the damage they inflict. They keep the art up on the third floor of the museum, and currently have a major display devoted to the first world war, which they claim is the largest of its type for nearly a century. It’s full of expected names, shown in some detail. But the ambience is wrong: there is something utterly deadly about those third-floor galleries (appropriate in a war museum, I suppose), which kills exhibitions stone-dead. However great the art — and there are masterpieces to be seen — it suffers badly from being shown there.

The display is split into two: one suite of galleries given over to the ‘Truth’ of the exhibition’s title, the other to ‘Memory’, but the division is more of a convenience than a real taxonomical distinction. Each set of rooms contains some 50 works, ‘Truth’ featuring a preponderance of works (both paintings and prints) by the cantankerous but brilliant Futurist C.R.W. Nevinson, including his famous painting of a machine-gun post, ‘La Mitrailleuse’. He was the first British artist to depict man dominated by the machines of war, whereas others, such as Paul Nash, concentrated on beleaguered man in shattered landscape.

A series of very beautiful, if grim, chalk and watercolour drawings by Nash chart the blasted heath of battlefield, from ‘Chaos Decoratif’ to ‘Sunset: Ruin of the Hospice, Wytschaete’. Then we move into a room of a dozen William Orpens offering a different kind of Edwardian take on the hostilities, in a very cool palette, blond to foetid green. Here we see ‘The Mad Woman of Douai’, a brilliant drawing of the end of a hero and a tank, and the surprisingly pale mud (given all that blood) of Thiepval, encompassing skulls and bones.

There’s a set of drypoint etchings entitled ‘The Dance of Death’ by Percy Delf Smith, a Royal Marine and one of the less familiar names here. And then, by contrast, there are three very peculiar paintings by Austin Osman Spare, praised for their ‘grizzly truthfulness’, done in a form of heightened hallucinogenic realism suitably apt for such horrors. Across the hall to ‘Memory’, the first room of which is dominated by the large ‘Oppy Wood’ painting, an early masterpiece by John Nash, Paul’s younger brother, who is also represented by his even better ‘Over the Top’. Clarity of design meets hopelessness and the quality of unreality that borders on the surreal. Opposite is Eric Kennington’s masterpiece ‘The Kensingtons at Laventie’, a marvellous painting of great lambency in oil on glass. Here, too, is a bizarre George Clausen: ‘Youth Mourning’, a lovely naked girl on her knees, head bowed to the earth in a calm landscape. In time of war, there’s always room for the allegorical approach.

The second room on this side is devoted to the Vorticists and dominated by Wyndham Lewis’s great mechanical, insectile ballet, ‘A Battery Shelled’. Some of the best things here are by William Roberts, particularly his atmospheric ‘“Feeds Round!” Stable-time in the Wagon-lines, France’. There are other fine things — by Stanley Spencer, Henry Lamb, Randolph Schwabe and Sydney Carline. Also the impressive ‘Artillery Drivers in the Snow’ by Arthur Neville Lewis, a South African artist who trained at the Slade. And there’s a whole room at the top end of the suite easily missed through bad signage, which contains several sculptures of note, including Charles Sargeant Jagger’s huge plaster relief of ‘The Battle of Ypres’, and John Singer Sargent’s harrowing masterwork ‘Gassed’.

There is no catalogue for this show, which is, I think, a mistake, and the nearest thing to one is a £10 paperback Art from The First World War, published in 2008. Don’t buy this, it will only make you want to see things reproduced in it not currently on display. Far better to save your money for a really splendid catalogue — such as the hefty 240-page tome published by Liss Fine Art to accompany their fabulous Great War exhibition at Morley Gallery, just a few minutes’ walk from the War Museum. This catalogue costs £25, but is worth every penny, being packed with illustrations, anecdotes and history.

Liss Fine Art was founded in 1991 by Paul Liss and Sacha Llewellyn, and specialises in ‘the unsung heroes and heroines of British art from 1880 to 1980’. The firm operates from France and does a lot of dealing on the internet, but makes regular appearances in London, as well as taking an annual stand at the 20/21 British Art Fair at the Royal College of Art, Kensington Gore, SW7, this year running from 10 to 14 September.

The Liss show is the product of several years’ work and presents a range of art and artefacts that is almost overwhelming in its diversity and richness. The catalogue illustrates more than 200 items and there are many more exhibits from the distinguished collection of wartime objects of David and Judith Cohen. (These include trench art, commemorative ware and sweetheart brooches, many of which are displayed in four large free-standing cabinets over the road in the foyer of Morley College itself.)

At Morley Gallery, the paintings jostle with the photographs, the posters with sculptures, prints and drawings, the postcards with miniatures, silhouettes and ceramics. The catalogue is arranged thematically in three main parts: ‘Combat’, ‘The Home Front’ and ‘The Aftermath’, and, as the curators say, it is in the popular arts that they’ve found some of the most poignant and unfamiliar images.

I particularly liked some of the posters: the vast Frank Brangwyn lithograph ‘Field Hospital in France’, which Liss bought in three separate parts and reunited, is perhaps the most extraordinary. Outside, Lord Kitchener exhorts you to enlist from one of the gallery’s window displays (a lovely feature at Morley); in another are a group of small Brangwyn drawings and an army uniform; a moving religious triptych by Percy Jowett holds the eye in another; in a fourth are trench art tanks.

The gallery’s interior is equally fascinating, with a handwritten copy of the naval signal announcing the surrender of the German fleet; a dramatic little oil of a dance of red-gold flames in a patch of darkness (a Zeppelin shot down); a yellowish drawing of a gas bombardment; and a pugnacious greengrocer outside his shop, which bears the sign ‘Business as Usual During the Alterations of the Map of Europe’. And much, much more. The exhibition at Morley is a museum show, but when it transfers to the Strand Gallery (32 John Adam Street, WC2) for Armistice week (11–15 November), nearly everything will be for sale, with prices ranging from £50 upwards. Don’t miss it.