In 1969, Francis Ford Coppola decided to give a young, war-obsessed screenwriter named John Milius a shot. He paid him fifteen thousand bucks to write the definitive Vietnam War film. Milius stepped up and created a monumental, mammoth screenplay (source).
The script sat around for years, collecting dust on the shelf.
Eventually, Coppola secured financial backing, using his own company (American Zoetrope), United Artists, and producers Fred Roos and Gray Frederickson. Paramount, which had produced The Godfather films, also got on board. Dust off that screenplay, boys—we've got a Vietnam War epic. It was gonna be…well, epic.
With the Philippines' jungle standing in for Vietnam, Apocalypse Now took three years to make, way longer than anyone expected. The money people were wringing their hands as the film ballooned over budget, and Coppola almost lost his mind. Martin Sheen had a heart attack; Brando showed up not knowing a word of the script; the set was destroyed by a typhoon. Everything went wrong, and Coppola and the other producers assumed it was going to be a massive failure and titanic waste of money (see the "Production Design" section for more details).
In the end, the money people were free to calm down.
Even at three times over budget at $31.5 million, the film managed to gross $150 million worldwide. Everyone went home happy (except for Marlon Brando, who thought he wasn't receiving his royalty checks or something).