It's a commonality in more action oriented genre pieces for there to be an ensemble cast, and for an unspecified number of said cast members to be expendable.
Although this formula has its roots in earlier "siege" pieces such as Agatha Christie's And Then There Were None (1939) and Zulu (1964), the formula was perfected with the advent of the Slasher sub-genre.
That is, The Texas Chainsaw Massacre (1972) and Halloween (1978) established a structure of violence in which there is a lead protagonist, a "survivor girl", that is "safe" (most of the time), creating a guessing game around how many survivors there will be among the secondary characters. While some, if not most, Slashers only have a lone survivor (usually a female), at times they are accompanied by one or more survivors.
Since Slasher films are action oriented by nature, this formula has easily been transferred to other genres, sometimes back to the genres it appropriated them from in the first place. For example: Science Fiction, the Western, and War film.
Aliens (1986), Young Guns (1988), and Saving Private Ryan (1998) are effective examples from each genre. The first has three survivors (and half an android), the second has three survivors, and the third has three survivors. Bear in mind that each film has a literal "team" that comprises my narrowed argument, and any auxiliary characters (such as, say, Van Leuwen in Aliens) are independent of the thematic resonance of being considered a survivor of the main conflict.
In Aliens, the core team is comprised of the Marines, their advisor, refugee girl, and corporate liaison. Ripley is the Survivor Girl, so her fate is never in question (a tradition Alien 3 cleverly subverts, but that's for the Movie of the Day: Alien 3 thread). Newt, Hicks, and Bishop being survivors defines their relationship with, and importance to, the Survivor Girl. Newt is a kid and off limits, but she also confirms Ripley's role as mother. Hicks was the most in doubt, but serves as a relatively non-threatening love interest for Ripley, completing the nuclear family dynamic. Bishop, meanwhile, redeems himself, but only in the sense that Ripley didn't trust him even though his intentions were always sound.
Young Guns, by comparison, is more nebulous. The core team is the Regulators, starting off with seven and ending with three. Billy the Kid is the Survivor Girl in this case, accompanied by Doc and Chavez (Yen Sun is a non-entity, in that she is defined by her relationship with Doc and is not a Regulator). Billy is an obvious choice, as historically he survived the Lincoln County War and his living is a heightening of the rebellious spirit of the Old West that he personified, but the rest of the cast dies seemingly with a role of the dice. Doc is possibly the most well-rounded character in the cast, but his death could've been viewed as a tragic commentary on Billy's hubris. The same with Chavez, whose need to have children and continue his people cannot overcome the inevitability of the fate of the Native American in the United States. Perhaps the irony is their being the least loyal to Billy's cause, they are won over by his reckless leadership.
Saving Private Ryan is a clever reversal on Aliens, in that the latter intertwines multiple genres (Science Fiction and Horror) with War, but the former reverses the significance of the Survivor Girl. The team, here, is eight men that are sent to retrieve the macguffin that is Priate Ryan. It's obvious from the start that Tom Hanks, as Captain John Miller, is the Protagonist and Audience Identification Character. This is due to a number of reasons, ranging from the popularity of the actor to his leadership role and the questionable significance of the opening close-up and fade-in of a pair of eyeballs. Miller, however, does not survive the film. Edward Burns's Private Reiben, Jeremy Davies's Corporal Upham, and of course Matt Damon's Private Ryan learn a lesson from the death of the former schoolteacher. Reiben is left to question the value of following orders, Upham has learned the necessity of killing in war, and Ryan has been challenging to "earn this". Basically, carpe diem. The spirit of Miller, therefore, lives on in all three characters.
With that in mind, what are the best (and worst) examples of ensemble casts that are weeded out over the cast of a film? What does it say about the lead that this selection of secondary characters survived, and what does that say about the secondary characters?
