The Martian war machines were originally going to be walking tripods as they were depicted in H.G. Wells' novel, but George Pal didn't know how a tripod would walk and instead went with the flying machines.
The Martian war machines had about twenty wires running to each one. Some were for suspension and maneuvering, while others carried power to the various lights and mechanisms. This was produced before there were lightweight circuits and sophisticated radio controls.
George Pal initially planned to portray the Martians and their fighting machines similarly to how they appear in the original novel. However, after being informed by a United States Army technical adviser that the Tripods, as they are portrayed in the 1897 novel, would pose no real threat to a 1950s era human military, he opted to change the fighting machines. Namely, Pal chose to introduce the atom bomb-resistant deflector shields.
In one of the montages of destruction in the film, Martian fighting machines were superimposed over black and white footage of a lava flow destroying buildings in and around Naples, Italy, during the 1944 eruption of Mt. Vesuvius.
As an homage to Orson Welles and his famous "War of the Worlds" radio broadcast, on Sunday evening, October 30th, 1938, on radio, voice specialist Paul Frees appears on-screen as a radio reporter and does his famous Orson Welles's vocal impersonation.
The sound effects of the Martian war machines' heat ray were created from three electric guitars played backward. The sound of the Martian screaming after Forrester hit it was a mixture of a microphone scraping along dry ice and a woman's scream played backward. The former set of sound effects became widely used stock sound effects after the film was released. They are still in use.
Paramount Pictures always wanted to put out a stereo version of The War of the Worlds (1953) on home video, but couldn't do so because the only archival sound elements it did not have from the film were the ones of the Martian ships. Luckily, the makers of the War of the Worlds (1988) television series had to recreate the sounds of the Martian warships from scratch for the series, which Paramount used to finally create its stereo version of the science-fiction classic.
Filming was halted briefly, two days into filming, when Paramount discovered that its filming rights of the novel were only for a silent version. It was quickly resolved through the kind permission of H.G. Wells' estate.
Originally, the Martian war machines were supposed to walk on visible electronic beams. This was attempted by having electrical sparks emanate from the three holes at the bottom of the machine. This was quickly abandoned for fear of it becoming a major fire hazard. The first two shots of the first war machine emerging from the gully have this effect. During filming, the actors were under the impression that they were dealing with the walking tripod machines of the book. This explains the farmhouse scene when Gene Barry says, "There's a machine standing right along side of us." However, the results of the walking can be seen wherever the Martian machines fly throughout the film, even though the sparking effect was no longer used.
Two of the sound effects in this film eventually became iconic sounds in Star Trek (1966). The sound of the war machines hovering went on to be the sound of a hand phaser.. The sound of the "skeleton ray" as Dr. Forrester called it became the sound of a photon torpedo.
Orson Welles, who rose to prominence with his "War of the Worlds" radio broadcast during the evening before Halloween of 1938, on Sunday evening, October 30th, 1938, and scaring numerous radio listeners, was pressured into making this his first feature film, but he wanted no part of it.
When Major General Mann first meets Dr. Forrester, he refers to an earlier meeting in Oak Ridge. This refers to Oak Ridge, Tennessee, which was the home to three Manhattan Project plants that enriched and refined uranium during World War II for use in the first atomic bombs. Of the three, one (K-25) was in use until 1985, and one (Y-12) was still in operation as of 2010.
A figure of Walter Lantz's most popular character, Woody Woodpecker can be glimpsed in the branches of the tree the initial Martian cylinder meteor flies over. Lantz and George Pal were close friends and Pal always worked an appearance of Woody Woodpecker into each of his films.
Gene Barry later admitted that acting in the film was was very trying, since he never saw the Martian ships while filming his scenes and had to react blindly to special effects shots that were added later.
The key to the success of this film is Pal's decision to use life-size models rather than miniatures or Harryhausen's stop motion puppets. With the large size models he was able to get incredibly realistic, life-like movement that couldn't be achieved any other way, and up until this point, never had. This presented quite a bit of a challenge in getting the double exposure of the acetylene torches that he used as the cobra-head's ray to match the head's movement. Look carefully in scenes where the machines are shooting and moving at the same time. You will see one of the the cobra head pointed down while the ray is shooting straight ahead; in another shot, the ray shoots to the (screen's) right, but by the time the ray stops, the cobra head is already turned forward and dropped. In one shot the ray seems like it's coming not from the center of the red lens, but off to the side, possibly even from the edge of the head structure and not the lens. Despite these slight imperfections, this was considered a great achievement for SciFi in the 50s.
The prologue of the film shows paintings of the other planets in the Solar System, which the Martians examined and rejected as being unfit for habitation, finally selecting the Earth. The planet Venus, however, is neither shown nor mentioned (it would not be suitable either, as its surface is excessively hot due to an extreme greenhouse effect, is highly volcanic, and plagued by sulfuric acid rains). The paintings were made by Chesley Bonestell, as famous astronomical painter whose works were often published in books on astronomy and space travel in the 1950s.
In the farmhouse, when the Martian fled from Clayton and Sylvia, Charles Gemora, who had to control the Martian by kneeling in the costume, almost fell out of the back of the suit when one of the workers pulled the platform on which the Martian was kneeling out of the shot, too fast. If you look closely at the scene, you can see the Martian is tipping over slightly.
By way of acknowledging the part that Cecil B. DeMille had played in bringing the story to the screen, George Pal wanted him to narrate the film, but DeMille suggested Sir Cedric Hardwicke instead. Pal also paid tribute to DeMille in the film by having his film Samson and Delilah (1949) listed on the theater marquee early in the film.
In an apparent homage to the famous Orson Welles's radio broadcast, on Sunday evening, October 30th, 1938, when the hatch of the Martian machine begins to unscrew, the same technique, a metal lid being turned on a glass jar, was used to create the sound effect.
Although the exact location of the first Martian landings isn't clearly identified, geographical references in dialog from the film would place it in the Puente Hills, about 25 miles due east of Santa Monica adjacent to the Pomona Freeway, south of West Covina.
Two of the characters from Orson Welles 1938 radio broadcast (portrayed in the film by different actors), Professor Pearson (the main player in the radio broadcast), and the ill-fated journalist Carl Phillips, made brief appearances at the site of the first Martian landing, in New Jersey, on Sunday evening October 30th, 1938.
Production of this film was completed just as the transition from Academy ratio to wide screen was taking place. For this reason, though the film was shot at an aspect ratio of 1.37:1, and in fact was shown in the UK in this format, for US domestic release it was shown theatrically at the aspect ratio of 1.66:1.
Robert Rockwell appears, uncredited, as a State Trooper in the film. Rockwell was the male lead in Our Miss Brooks (1952). When that series changed it's format, Rockwell was replaced by Gene Barry, the lead in this film.
The images of each planet in the Solar System that appear at the beginning of the film are paintings by Chesley Bonestell which appear in the original 1949 edition of the book "The Conquest Of Space" by Willy Ley.
The number "three" recurs many times throughout the picture. The Martian cylinders are said to land in groups of three and there are three war machines to each cylinder. The Martians have three fingers on each hand and there are three pupils in the Martian eye. Early in the film, three men are instructed to watch the newly landed cylinder. Later, Dr. Forrester and two other men travel in a squad car to the cylinder. The lead fireman calls to headquarters: "Number three to D.O." At the conclusion, Forrester visits three churches before finding Sylvia.
The paintings seen in the beginning of the film were done by Chesley Bonestell, whose art hangs in the National Air & Space Museum. Bonestell also helped design the Golden Gate Bridge and the Chrysler Building.
The trivia items below may give away important plot points.
The disintegration of Colonel Heffner took 144 (a gross) individual mattes. Earlier in the scene, the stuntman who portrayed the soldier catching on fire was badly burned from the flames getting out of control.
The Martian machines were models suspended from wires. For the final sequences where the machines die, they are shown crashing into telegraph poles - this allowed the filmmakers to hide the suspension wires with the telegraph wires.
The scripture Pastor Matthew was reciting before being disintegrated by the Martians, is Psalms 23 of the Original King James Version of the Bible. (Before, different versions were created, replacing old English with 21st Century English. 4 SAMPLES: Thou = You. Yea = Yes. Wot = Know. Ass = Donkey.)