Tom Cruise and Steven Spielberg's latest film, War of the Worlds, is the latest example of Hollywood's enduring fascination with alien invasion.
By Neil Smith
BBC News entertainment reporter
Steven Spielberg's blockbuster is one of numerous interpretations of HG Wells' classic 1898 novel, which has also inspired a best-selling album, a TV series and Orson Welles' legendary 1938 radio broadcast.
Tom Cruise stars in the new film version of War of the Worlds
But it is a testament to the power of Wells' apocalyptic vision that it has also spawned an entire sub-genre of science-fiction films that use the notion of alien incursion to tap into societal fears and phobias.
The original War of the Worlds was seen at the time of its publication as a critique of Europe's attitude towards its African and Asian colonies.
Yet its depiction of powerless humans under attack by the Martians' vastly superior weaponry can also be read as a cautionary warning of the dangers posed by advancing technology.
The aliens' three-legged fighting machines, for example, can be viewed as a precursor to the tank, while their unchecked advance across the Home Counties may have tapped into contemporary concerns over Germany's escalating military might.
Invasion of the Body Snatchers was released during the McCarthy era
These concerns came to the fore again during the Cold War, in which the threat of malevolent extra-terrestrials echoed paranoia over Communist infiltration in the American homeland.
Invaders from Mars, Howard Hawks' The Thing from Another World and The Beast with a Million Eyes were just a few of the sci-fi B-movies that saw Earth terrorised by bug-eyed, green-skinned monsters.
However, the limitations of the genre did not stop some directors using it to make more sophisticated parallels.
In The Day The Earth Stood Still, an alien visitor tells the world that nuclear proliferation will result in mankind's destruction.
And Invasion of the Body Snatchers uses the arrival of "pod-people" in small-town America to reflect the hysteria whipped up by the McCarthy era witch-hunts.
From the late 1960s onwards, however, alien visitations took on a more benign flavour.
The tide began to shift with Kubrick's 2001: A Space Odyssey
In 2001: A Space Odyssey, director Stanley Kubrick proposed that all human advancement is steered by benevolent forces from the stars.
And in Close Encounters of the Third Kind and ET the Extra-Terrestrial, Steven Spielberg cornered the market in gentle visitors more intent on studying man than annihilating him.
The phenomenal success of these films suggested we had seen the last of hostile alien takeovers.
But 1996's Independence Day brought the genre full circle by showing gigantic UFOs using their awesome firepower to destroy such iconic landmarks as the Empire State Building and the White House.
"Now that's what I call a close encounter!" crowed Will Smith's cocky pilot as he thumped a cowering alien, his triumphalism perhaps echoing America's newfound self-image as the world's policeman and guardian.
It hardly needs saying that the globe's ultimate victory is achieved through a US-led coalition.
ET the Extra-Terrestrial presented a more benign alien visitor
Tim Burton's Mars Attacks! and Men in Black, also starring Will Smith, offered a more tongue-in-cheek view of aliens among us.
But the terrorist attacks of September 2001 ushered in a new era of anxiety and introspection, which was reflected in a fresh wave of sci-fi thrillers.
With their portraits of dysfunctional American families uniting against an external menace, M Night Shamalyan's Signs and Spielberg's War of the Worlds can be seen as responses to the post-11 September angst prevalent in the US.
United we stand, divided we fall seems to be the message - a sentiment that can apply equally to genuine threats and fantastical ones.