This is an exhibition whose topic is easy to describe. War posters are instantly recognisable, and some have reached iconic status, becoming objects for satire and appropriation. Alfred Leete’s poster of Lord Kitchener with the pointy finger - ‘Your Country Needs You’ - is perhaps top of the pile, and so fittingly is one of the first posters on display here, but there are plenty more. ‘Careless talk costs lives’, ‘dig for victory’ - the captions on these posters have become memorable slogans, even for those who didn’t live through the war.

‘Weapons of Mass Communication’ isn’t just about the well-known posters though. The exhibition is filled with posters from across the globe, giving an insight into the styles and propaganda devices used in other countries. Interestingly, some of the design styles seem to have crossed enemy lines, with British poster designs employing some of the ideas of the Germans.

The exhibition is arranged thematically, with sections such as symbolism and ‘civilian lives’, although there’s also a loose chronology at play. Some of the posters are huge - billboard sized - and they’re hung tightly together, the effect of which can be almost overwhelming at times. There’s not a huge amount of narrative available, the text is restrained to a title, date and country for each poster, with a short couple of paragraphs for each section. At times, this lack of explanation is frustrating, particularly for the foreign-language posters, but on the whole the posters speak for themselves.

Towards the end, there’s a marked shift away from the functional posters of war-time propaganda towards the more sophisticated, and cacophonous, posters of political activism. Some of these are just as iconic, particularly those of the recent anti war movement, the red splat of which is echoed in the exhibition identity. These, and others from recent history, act as powerful reminders of the times we’ve been through.

Ultimately, the conclusion we come to from viewing this exhibition, is that posters can indeed be a tool of mass communication, but they can also come to stand in as a symbol to represent a moment in history.

Weapons of Mass Communication: War Posters is on at the Imperial War Museum in London until 30 March 2008. Admission free.