All-Star Cast: More than Ocean's 11. According to one critic, "everyone in Hollywood auditioned for the film," because Malick was a mysterious legend who hadn't made a film in 20 years.
Sean Penn, Adrien Brody, Jim Caviezel, Nick Nolte, Woody Harrelson, Ben Chaplin, John Cusack, John C. Reilly, George Clooney, John Travolta, Jared Leto, Tim Blake Nelson, and John Savage. (Billy Bob Thornton, Martin Sheen, Gary Oldman, Bill Pullman, Lukas Haas, Viggo Mortensen and Mickey Rourke also starred, but didn't make the final cut. Rourke in particular felt betrayed by this as he felt his work on this film to be the best of his career).
"Malick began adapting The Thin Red Line on January 1, 1989. Five months later, the producers received his first draft that was 300 pages long ... Malick spent years working on other projects ... By January 1995, Geisler and Roberdeau were broke and pressured Malick to decide which one he would complete ... In April 1997, three months before filming, Sony pulled the plug while crews were building the sets... 20th Century Fox agreed to put up $39 million of the budget with the stipulation that Malick cast five movie stars from a list of 10 who were interested.
Malick specifically cast actors (dozens of famous actors) who look like each other, to put forth the message that all the soldiers are part of a unit and fundamentally different aspects of the same person. With lots and lots of (then-unknown) actors cast because they look very similar to lots and lots of (famous) actors who all wanted to appear in a Malick film, and with most of the dialogue being internal monologue, you have a situation where it's easier for people who haven't read the book to tell the characters apart by the actor playing them.
A few flashbacks and somewhat surreal sequences reveal that Ben Chaplin's character is married to Eowyn.