Next month, Iron Man will be unveiled as an unlikely ally of the United Nations. But don't be surprised: comic-book superheroes have been co-opted for propaganda purposes since the 40s, says Paul Gravett

Got a problem with fascist dictators, drug addicts or people not sticking their empty cereal packets in the recycling bin? That sounds like a job for... Superman! No, seriously. Since they were born on the eve of the second world war, America's superheroes have been enlisted for all sorts of undercover propaganda duties, from promoting patriotism, war bonds and recycling (even of comics themselves) to warning about health, drugs and landmines. So it's nothing new that Iron Man, the latest in Marvel's pop-icon pantheon to hit the big screen, is coming to the rescue of the United Nations. In a specially customised comic book, Ol' Shellhead and his costumed cohorts will battle that most terrible of supervillains, a tarnished public image, by demonstrating the UN's positive, proactive roles. Will it work? It's debatable: over the years these earnest, message-laden stories have not always been too effective as weapons of mass persuasion.

When it comes to propaganda, superheroes were probably at their most convincing in the early 40s, when they and their frequently Jewish creators and publishers, were tackling Hitler himself long before America entered the fray after Pearl Harbor. Seventy years ago this year, two young bespectacled Cleveland Jews, Jerry Siegel and Joe Shuster, saw their nerdish fantasies published on four-colour newsprint as Superman burst off the pages of the first Action Comics and sparked a battalion of imitators. Their Man Of Steel started out as a champion against corrupt employers and other scoundrels but he and other superheroes would soon find the perfect bad guys in the Nazis and the Japanese.

For the February 27 1940 issue of Look weekly, Siegel and Shuster were commissioned to create a two-page expose showing How Superman Would End The War. After he pummels Germany's fortifications on the Siegfried Line, Superman grabs Hitler and Stalin and flies them to Geneva where they are found guilty of "unprovoked aggression against defenceless countries" by the League Of Nations, forerunner of the UN. This condemnation of the Nazis seems to have worked as propaganda. It reportedly infuriated Joseph Goebbels, himself a master propagandist, so much that he angrily proclaimed "Superman is Jewish!" in a meeting. Not long after, on April 25 1940, the SS newspaper Das Schwarze Korps ran an anonymous full-page counter attack, probably written by Goebbels, denouncing the "intellectually and physically circumcised" Jerry Siegel as "a Colorado beetle" who "works in the dark, in incomprehensible ways" on American children.

In his Look strip, Superman was restrained from giving the captive Fuhrer "a strictly non-Aryan sock on your jaw". A year later, another Jewish partnership, New Yorkers Joe Simon and Jack Kirby, unleashed their super-patriot Captain America, garbed in the stars and stripes flag, who finally gave Hitler that threatened punch on their first issue's front cover. This was too much for some American Nazi sympathisers and opponents of their country entering the war. Simon and Kirby's studio became the target of hate mail, obscene phone calls and sinister types lurking outside, until mayor Fiorello LaGuardia himself rang Simon to assure him of round-the-clock police protection, saying, "You boys over there are doing a good job. The city of New York will see that no harm will come to you." Once the war was won, however, Captain America hung up his shield. Somehow his comeback as a 50s "commie basher" in the Cold War and Korea never caught on.

The 60s and 70s saw costumed crime-fighters getting involved in real social issues. Stan Lee ignored the Comics Code Authority's regulation forbidding any mention of drugs and wrote a warning about their dangers in Spider-Man. Soon after, Denny O'Neill and Neal Adams confronted the same issue, with the shock revelation that Green Arrow's trusty sidekick was an addict. The fact that he was called Speedy might have given us a clue.

Several public service bodies have used famous superheroes to put across their messages. Notoriously, in one Spider-Man comic, it's disclosed that as a youngster his alter ego Peter Parker was a a victim of homosexual molestation, though this revelation seems to have been written out of the webslinger's "official" biography. Despite the "real" struggles with the bottle of Iron Man's alcoholic alter ego Tony Stark, to be explored in the movie's sequel, he's not yet been a spokes-hero in an anti-boozing comic.

Today Cap, Spidey and their cohorts are back in favour with those in high places and not just at the UN. In 2005, Donald Rumsfeld puffed out his chest next to actors dressed as Captain America and Spider-Man to launch the first of Marvel's free comic books for America's armed forces in Iraq, Afghanistan and elsewhere. Reflecting our more complex political times, their messages are curiously oblique. In the fifth and latest issue of The New Avengers: The Spirit Of America (it is left to us to guess what they are avenging), Bin Laden is nowhere to be seen. Rather, the only villains are Marvel's own stock Axis Of Evil, Hydra or AIM (Advanced Idea Mechanics), now rebranded as "terrorist organisations". No specific warzone is given, only "overseas". You may have heard that Cap was shot dead (don't worry, death is only temporary for superheroes - ask Superman), but the comic closes with a last patriotic message: "Heroes don't live forever. And when they're gone, that's when we all have to step up and do our duty. For we are all Americans. Goodnight and be safe." Easy for Cap to say when he's been given a strength-boosting serum to transform him into a Super-Soldier. Despite the cover lines that "Marvel salutes the real heroes, the men and women of the US military", the two ordinary soldiers featured here, a brother and sister, still need the combined superpowers of Cap, Silver Surfer, Ghost Rider and Punisher to pull them through. Not the most inspiring message perhaps for our boys and girls on the frontlines.

As for the UN, superheroes have come to its rescue before. In November 1967, The Justice League Of America featured the UN symbol on the cover of issue 57, in a very right-on plea for racial harmony called "Man, The Name is - Brother!" The UN even had their very own team of superheroes devised by Wally Wood for Tower Comics in the 60s. Called the THUNDER Agents (The Higher United Nations Defence Enforcement Reserves), they were led by Dynamo, dressed in the UN's blue and white colours. Rather than relying on Marvel's characters, the UN could have resurrected this team, but THUNDER Agents vanished after only 20 issues and only aging comic collectors remember them now. Instead, maybe the UN should take a tip from Unicef, who have signed up the Smurfs, also decked in regulation blue and white, to be their ambassadors for children's rights this year. Sounds like a job for... Papa Smurf!

· Iron Man is out on May 2

Comic relief

Damon Wise rounds up this summer's other superhero blockbusters...

Iron Man

Rich, troubled industrialist Tony Stark is a pioneering inventor who devised his rocket-powered, bullet-firing, all-powerful suit of armour while imprisoned by terrorists. Suitably, this excitable, brilliant playboy will be portrayed by Robert Downey Jr in the film by Jon Favreau, of Swingers fame, who wants to emaphasise the "billionaire bachelor" side of things.

Hellboy 2

Though the first was a flop, Sony have let Guillermo Del Toro serve up a second serving of the demon who flexes his crusty red Right Hand Of Doom against wrongdoers.

Speed Racer

After the drubbing meted out to their grim brace of Matrix sequels, the Wachowksi brothers dove head first into the playful, neon world of Speed Racer, a semi-animated take on the 60s cult Japanese anime series Mach GoGoGo.

The Incredible Hulk

Nobody asked for a sequel but they got one anyway. The Incredible Hulk stars Edward Norton as Dr Bruce Banner, a scientist contaminated by the effects of a gamma bomb, which turn him into a raging green giant whenever he's angry.

Hancock

This dark comedy stars Will Smith as a reluctant flying crime-fighter, a lazy, alcoholic and misanthropic strongman, whose inept heroics are fast destroying downtown LA.

The Dark Knight

Bruce Wayne returns in Christopher Nolan's sequel which promises to be darker and better than the first, with Batman under threat from Heath Ledger's deranged Joker, little realising that his ally, the DA, Harvey Two-Face Dent, isn't playing with a full deck either.