Emmerich and Devlin decided to expand on the idea by incorporating a large-scale attack, with Devlin saying he was bothered by the fact that "for the most part, in alien invasion movies, they come down to Earth and they're hidden in some back field …r they arrive in little spores and inject themselves into the back of someone's head." Emmerich agreed by asking Devlin if arriving from across the galaxy, "would you hide on a farm or would you make a big entrance?" The two wrote the script during a month-long vacation in Mexico, and just one day after they sent it out for consideration, 20th Century Fox chairman Peter Chernin greenlit the screenplay. Pre-production began just three days later in February 1995. The U.S. military originally intended to provide personnel, vehicles, and costumes for the film; however, they backed out when the producers refused to remove the script's Area 51 references.