In Outlaw Star, the crew is a Band of Brothers. Even though they all met under different circumstances and some at first didn't like the main character or each other, they all eventually become allies.
Justy Tylor from Irresponsible Captain Tylor sees the crew of the Soyokaze as this ("You're like everyone else on the Soyokaze is to me...You're my crew...and you're all important to me"). Some of the Marines might beg to differ, though. Even so, they will face against the entire UPSF to save him. Twice.
The main cast of Cowboy Bebop becomes this, but only very late in the series. It's their becoming a proper Band of Brothers, rather than just a group of people sharing a ship, that makes the ending as poignant and difficult as it is.
Gatchaman. One of the original Five Man Bands, the Science Ninja Team may fight, argue and generally crawl all over each other's nerves, but when push comes to shove they'll go through hell for one another. Arguably the origin of the Super Sentai version of the trope.
The Yang team in Legend of the Galactic Heroes: being betrayed by their own government, facing the full might of Reinhart's armies, even losing their leader, their group is not going to break.
One Piece. The Straw Hats aren't just a crew. They're family.
Also, Ace, Luffy, and Sabo, (before Ace and Sabo died), fought together in the forest that they grew up in. They beat up animals for food and men many times their age as well. Even until the end, they never lost their brotherly love and bond between the three of them.
The three Gun-swordsmen in Brigadoon: Marin and Melan are supposed to function like this, though differences of opinion get in the way. (They're based on the Three Musketeers.)''.
The various teams in the Fairy Tail guild like Shadow Gear and the Raijinshuu are already True Companions and the guild is pretty much a very large set of True Companions bordering on a Band of Brothers due to sheer size and the often dangerous nature of their jobs. The best example however is the Guild Alliance formed to combat Oracion Seis. Long after the dark guild was defeated, the members from Blue Pegasus, Lamia Scale and Cait Shelter join or are on very good terms with Fairy Tail. When Fairy Tail was in need, they immediately came to their aid spending much time and effort to locate the missing Tenrou Island. When the core cast came back after the time skip, members of both guilds quickly pay them a visit to renew old friendships.
The 104th Trainee Corps in Attack on Titan just after the Battle of Troist. Most of them even follow Eren into the Survey Corps against their own wishes. Though three of their companions (Bertolt, Reiner and Annie) happened to be the enemy while Ymir defected to their side to protect Krista, the remaining members became part of Levi's new squad.
The various teams of X-Men display this trope at times. Fantastic Four would qualify as well, if three of its four charter members weren't already directly related by blood or marriage.
The various Teen Titans teams are just as much a surrogate family as they are a crimefighting team. This is especially true of the "Original Five": Robin, Wonder Girl, Kid Flash, Speedy, and Aqualad. This was carried over in the cartoon.
In fact, Nightwing and Arsenal's Outsiders were formed in a deliberate attempt to avoid creating a Band of Brothers. Naturally, given the characters and the circumstances, they failed.
This is how the Justice Society of America is set up. The four old men of the team (Hawkman, Wildcat, Flash I and Green Lantern I) have all lost children or otherwise had problems being fathers, as elaborated upon in the "Princes of Darkness" arc. Many other characters have parental issues, such as Jesse Quick/Liberty Belle II (dead father), Hourman III (absentee father returned from the dead), Stargirl (stepfather is crimefighting partner, father is a dead criminal) and Damage (son of the original Atom, created by Vandal Savage). Ma Hunkel, the original Red Tornado, is the maternalglue keeping the team together.
Of all the ties formed in the Avengers long history, none match those between Captain America, Iron Man, and Thor. The team is always at its strongest when these three are in it, and any two of them would lay down their lives for the third without hesitation. This is what made the Cap/Iron Man conflict in Civil War so devastating stupid; one has to wonder if it might have been averted if Thor hadn't been dead at the time.
The Legion of Super-Heroes - particularly the Founders Three, Cosmic Boy, Saturn Girl, and Lightning Lad/Live Wire - and, separately, the Legion of Substitute Heroes. In the case of the latter, there is at least one instance of one of the Substitutes turning down an invitation to join the Legion proper out of loyalty to the other Subs.
Oddly enough, Flash'sRogues Gallery seem to have this thing going for them, especially when Geoff Johns is writing them. They're still terrible people, and will do terrible things if you turn your back on them, but when Captain Cold leads, "There's nothing more important than family (except maybe revenge)."
More than any other Justice League lineup, the Justice League International is always portrayed as the one place these ragtag group of B-listers ever truly belonged.
As noted in the Anime section, Roy Mustang's unit fits the trope, as shown in the Elemental Chess Trilogy. Jean Havoc even invokes the trope by name, thinking of how the unit is still "a band of brothers (and one sister, of course)" and he'd willingly die for any one of them.
The Survivors of Blind Mans Bluff are this. They'll never, ever leave anyone behind and they will fight to the death to save each other. If there's one thing you know, it's that they're going to weather through the zombie apocalypse together.
The ending, and in some ways the entire point of Zombieland is the forging of one of these between the survivors.
Emphasized in the Cambridge Spies, though in real life they were not such a close group emotionally.
The eponymous rodents in G Force are one hell of a Band of Brothers. The original group is Darwin, Juarez Blaster, Speckles and Mooch. Later, Speckles removes himself from the group by faking his own death. It's made explicit by the big fight scene at the end, when Speckles realizes that he doesn't need to avenge his family; he's already got one in the form of G-Force, Ben and Marcy, and possibly Hurley too. Darwin actually references this during the original sneak-in to Saber's house; "We leave no rodent behind."
The Burns Gang of The Proposition are a perfect example of an evil version of this trope. Arthur considers all of them to be brothers, including the ones who aren't his genetic brothers, one of whom is even of a different race. He truly loves them all, and has not a single cruel word for any of them. When told that his youngest (genetic) brother has found a girl and wants out, he is completely supportive. And if you're not his brother, you're liable to get shot, knifed, kicked to death, robbed, or possibly raped.
Dave: They tried to make me talk. I gave 'em nothing.
Frank: You don't know me. You don't owe me anything. I've brought you nothing but trouble. Why are you ready to die for me?
Dave: Because... you're one of us. You're family.
Saving Private Ryan: Private Ryan, asked by Captain Miller what they should tell his mother if he stayed to fight, said to tell her, "When you found me, I was here, and I was with the only brothers I have left. And that there was no way I was deserting them. I think she'd understand that."
The main cast also form its own Band of Brothers, with Miller as a stern dad and Horvath as big brother.
The eponymous mercenaries in The Expendables are this, to the point that they take the member who betrayed them back by the end of the movie.
In Robin Hood, after 10 years together in the army, Robin's friends choose to stick around even after Robin urges them repeatedly to go their own ways.
Played for laughs at the beginning of Another Country when Rupert Everett's Russian spy character uses the quote in a conversation with a young female reporter. She does not recognize the lines, highligthing the differences in age and education between the two. Also, the trope is inverted or at least used with some irony because "band of brothers" here refers to members of the Guy Burgess traitor ring, aka the Cambridge Five.
Orson Scott Card calls this a "jeesh" (though only in the Ender's Shadow series), but still essentially the same thing in Enders Game. The fact that they're a group of military super-geniuses makes them particularly dangerous. Also referred to as a "jeesh" in Empire.
The core of the eponymous mercenary band in Glen Cook's The Black Company is a Band of Brothers, and it's the only way the survive all of the crazy shit that happens to them.
The Fellowship of the Ring from the Lord of the Rings ends up like this, especially the four hobbits and the three hunters. In fact, many novels that are based on small long-term groups with fixed rosters that do D&D-style adventuring result in a Band of Brothers of sorts.
This shown when, despite Boromir's betrayal, the team goes instantly to rescue him. Also, Boromir fighting past when he should have died, to defend two of their number.
Roran begins seeing his various groups of fellow soldiers like this in Brisingr, although his most notable relationship is with Carn. Furthermore, Eragon and Saphira have been this since day one, and Eragon's larger Band of Brothers not only includes Saphira and Roran, but also Arya, Orik, Nasuada, and Katrina. Granted, Roran is his cousin that may as well be his brother, and Orik is his foster brother.
The stormtroopers who become the Hand of Judgment in Timothy Zahn's Allegiance. An Imperial Security Bureau officer comes down on one of them for refusing to shoot unarmed civilians and in the process aims a blaster. The trooper's training kicks in and he kills the officer. The trooper's four friends collectively go "Oh Crap" and very quickly decide to go with him as he leaves, since he'll be executed if he stays and they'll probably be executed too, for associating with him. Although they argue, they stay together even later.
Lampshaded in the Legacy of the Aldenata: "We few, we happy few, we band of brothers. In years to come, men at home now in their beds will think of this day and do you know what they'll say? 'Jesus, I'm glad I wasn't with those poor doomed ACS assholes or right now I'd be dead'. But what the hell, that's why they pay us the big bucks. Board ships."
In the Starfire novels by David Weber and Steve White, the Orions have this as an ideal for their armed forces — farshatok, which roughly translates as warriors who work together like the fingers of a fist.
In C.S. Goto's Blood Ravens trilogy, Gabriel confronts another Blood Raven captain with his friends in the room, because he knows he can trust them to have his back even against the other captain — that's why they were his friends.
Ellie Linton and her friends in The Tomorrow Series are a close Band of Brothers. Later on, they even bond with the feral children they've taken in, to the point that Ellie nearly doesn't want to let them be sent to New Zealand—-and one of the ferals, Gavin, does stay with them.
The French Corps of Marshals is often presented as this.
Anti-social and people hating Sasha Hunter grows to appreciate the bond she shares with her team mates in Greek Ninja, and it becomes obvious she would give her life for any one of them, even though she couldn't stand them to start with.
Live Action TV
Every version of Star Trek has this, from the original to the latest incarnations.
Star Trek: The Next Generation had a bit of this going on, particularly during the first season, before the characters had worked each other out. Riker was uneasy about their second officer, Picard had to tell people not to let him "make an ass of himself" around children (and shouted Wesley out in the very first episode, thus enraging Wesley's mother with whom Picard already had an uneasy relationship), Worf disliked everyone (but especially Data), and Troi and Riker had Uncomfortable Ex's syndrome. But within a matter of episodes (and fairly ridiculous episodes at that) it became obvious that they'd all pretty much die for each other.
Star Trek: Deep Space Nine and Star Trek: Voyager both feature crews of people who don't even want to be on the same ship/station with each other, but over the courses of each series have wound up going as far as disobeying orders to save one another.
Angel: We've been pushed to the edge so many times; done things we were sure could never be forgiven. But we're always there for each other when it counts. We've never let the darkness win. And it's not because of the Powers That Be or the super strength or the magical weapons. It's because we believe in each other, not just as friends or lovers, but as champions. All of us, together.
The crew of Serenity in Firefly in particular will do just about anything for each other. Even Simon Tam and Jayne Cobb, who hate each other, have saved the life of the other at least. Not to mention this exchange after Mal and crew save River from being burned at the stake in the Big Damn Heroes moment that named that trope:
Mal: Cut her down!
Patron: The girl is a witch.
Mal: Yeah, but she's our witch. * [KA-CHINK!]* So cut her the hell down.
Simon: Why did you come back for us?
Mal: You're part of my crew.
Simon: But you don't even like me?
Mal: You're part of my crew. Why are we still discussing this?
Jayne: What're you takin' it so personal for? It ain't like I ratted you out to the feds!
Mal: Oh, but you did! You turn on any of my crew, you turn on me! But since that's a concept you can't seem to wrap your head around, then you've got no place here. You did it to me, Jayne. And that's a fact.
In turn, the rest of the crew showed their own unblinking loyalty to Mal in "War Stories", when even Simon and Kaylee took up arms to save him.
Kaylee: If it were any of us, Cap'n wouldn't hesitate.
Ariel also has Simon going off to save a dying man, risking capture and leaving River in Jayne's care - which he probably wouldn't have done if he didn't actually trust Jayne to get River to safety should anything happen to him. One can't help but wonder how the extent of Simon's trust factored in Jayne's decision to save Tams instead of simply making a run for it at the first opportune moment.
Any Super Sentai or Power Rangers team. (And Power RangersReunion Shows make it seem that all teams are like an extended family... again, if you remember that it doesn't necessarily mean you like each other.)
Battlestar Galactica: If adult adoption were legal, Bill Adama would declare his entire crew as his children... though as the series wears on, his fatherly patience is repeatedly tested.
Farscape: The Moya crew sure qualifies. Certainly it's a very screwed-up Band of Brothers, but it's still a Band of Brothers. Pilot and Moya in particular are the first to feel this way, but as the series goes on, they get closer and closer until eventually their one rule is "look out for the family, at all costs."
Which was a catch-phrase at the SGC earlier (see the episode Abyss for a perfect example of how far this can be taken and understood). The members of the team become each other's best friends, confidants, and essentially nothing will cause more angst than when one is in trouble, wounded, or presumed dead. Stargate SG-1 epitomizes the Band of Brothers trope. Major Carter even says to one of the other characters, "We were a team. No one can even begin to understand what that really means." And calls Daniel's death(presumed)/ascension one of the worst things she's ever been through. And, let's face it, she's been through a lot.
Teal'c: You are like a brother to me, O'Neill.
O'Neill: Aren't you like, eighty...?
Teal'c: A younger brother perhaps, but that is not the point.
In Burn Notice Michael Westen is closer to Fiona and Sam than he is his actual family, having placed his life in their hands more than once in their long history as spies. Over the course of the show, he has to learn to to re-relate to and even trust his mother and brother Nate as well as he does his friends.
The A-Team. From the almost father-and-son-like relationship between Hannibal and Face to Vitriolic Best Buds B. A. and Murdock, to Face and Murdock's Odd Friendship (really, how can a suave con man and a crazy pilot be best friends? Just ask Face and Murdock), you can tell they're more like a family than just a team of ex-military acquaintances. For instance, in the Season 2 finale, when Murdock gets shot in the chest during a job in the middle of nowhere, they pull out all the stops and even face possible capture by the military in order to save him. They even include the "we can insult each other, but when outsiders do it we close ranks" bit.
"Band of Brothers". They even named the mini-series after the trope naming quote. Fittingly this series EPITOMISES a band of brothers. Winters, Nixon, Spiers, Bull, Lipton, Malarkey, Luz, Martin, Liebgott and many many more. And from what we see, the actors also lived up to this trope during the boot camp prior to filming, and still get together once a year for reunions.
The Leverage crew has elements of this. Note how protective everyone gets when Parker is in trouble, or how they all get together to save Nate even when they've officially split up.
A common thread of the CSI: Crime Scene Investigation series-pick any of the three and watch how protective they get when one of their own is in trouble and how they look out for each other all the time.
In "Epitaph One", we see Adelle caring for Topher (who has gone insane) like a mother for a child.
The end of "The Attic" seems to signal the point where all the main characters realize that they're on the same side. Laurence Dominic is probably a member too, though he's still stuck in the Attic.
Boyd outright states that they're family in "The Hollow Men." Unfortunately, he's been revealed as the Big Bad by this point. Tony and Priya say the same thing, and because of Boyd's previous usage of the term, Echo/Caroline tells them to call them anything but that.
Robert Crawley, 6th Earl of Grantham, on Downton Abbey and his valet, John Bates. Both served in the Second Boer War; Bates was his batman (a military bodyguard-cum-valet for an officer). Lord Grantham is intensely protective of Bates, keeping him on as his valet even though his leg injury makes it much more difficult for him to do a valet's job, backing him up on the occasions that downstairs spats reached his attention, and, most vitally, allowing Bates to use the Crawley family lawyer Mr Murray after he is accused and convicted of Mrs Bates' murder. For his part, Bates tries his best to serve as Lord Grantham's eyes and ears downstairs.
No doubt the both of them have other such friends from the Regiment, but we never see them.
Sibuna from House of Anubis. Despite any fights the group may have they are shown to be incredibly loyal to each other, risking lives on almost a daily basis for another member who needs it. Not exactly a band of brothers though, as it's, as Amber puts it, "Three girls and two men. Well, boys." However, now it's three boys and two girls, but the point still stands.
To a lesser extent the whole of Anubis House could be seen as this. Loyalties are definitely less obvious and many times the students to turn on one another, but when things get serious you can expect everyone to work together, especially if one of their own is being threatened.
Flash Gordon, Dale Arden, Hans Zarkov, Thun, Barin, Aura, and Vultan.
Burning Wheel has a standard intro/demo scenario, The Sword, about what happens when the adventuring party gets the loot and no longer has anything holding their disparate intentions for it together. Hint: it's also often used as a combat demo, and there are no characters or monsters except the PCs.
Despite the setting, Warhammer 40,000 even manages to demonstrate this trope with the Space Marines. Nothing is more important to them than loyalty to their Battle Brothers and fealty to the Chapter, and aside from the God-Emperor himself and the founding Primarch they recognise no authority other than their Chapter Master. This is why the Horus Heresy is considering so tragic, as conquering solar systems and crushing civilisations was perfectly fine, but turning against and fighting your brothers was inconceivable.
Tau units are sometimes bonded together in the Ta'lissera ritual, which translates as 'covenant', 'bond', or 'marriage' depending on the source.
In BattleTech this one of the defining traits of Clan Ghost Bear, Hell's Horses, and Star Adder. Whilst most Clans are very elitists and like segregating great warriors from Cannon Fodder, these Clans encourage camaraderie, and treat everyone as equals, regardless of their role.
One of the reasons that the plot of Othello works is that Iago is part of Othello's band of brothers, and thus it is assumed that he is playing the role.
In the vast majority of RPGs where the player is accompanied by a party of disparate characters, they will usually become this by the halfway point of the game. If the game has a Karma Meter this will often only be the result for the good path, whereas the evil path will have any characters who survive being more like minions.
Rainbow Six pulls this in Vegas with Bishop, especially with Logan and Gabe where she stresses they are a team and a family. In the final mission where Bishop is defying orders to go after a traitor, Logan says the same thing back to Bishop when he shows up out of the blue to provide backup. Her reply? "Who said that horseshit?"
Philanthropy in Metal Gear Solid 4: Guns of the Patriots. Ho Yay aside. Sure, Old Snake has the social skills of a toad, sure, Otacon is a walking civilian form of PTSD from sexual abuse and the tendency for people he cares about to die, and sure, Sunny has never left the Nomad to have anything resembling a normal childhood...but they're all in it together.
The Cobra Unit from Metal Gear Solid 3 joined the Boss when she left the US for the Soviet Union. The Fury in particular had a dying speech covering the relationship between her and them.
Dead Cell from Metal Gear Solid 2, or at least Vamp and Fortune, were something of a Band of Brothers. This is mostly insinuated through the way Fortune acts and what she reveals more than anything else, but there was some sort of comradery there.
Delta Squad from Gearsof War, especially Marcus and Dom. To some extent, this applies to the entire COG army.
Dom: Do we have time?
Marcus: They're Gears. We'll make time.
Modern Warfare 2 has this by the end, between Soap, Price and Nikolai. It's implied that Roach and Ghost were well on the way towards being a part of it, but their deaths cemented it for the first three.
The mercenaries of Team Fortress 2 are Sociopathic Heroes at best, but that doesn't stop them from working together like a well-oiled machine of death who are quick to genuinely thank and complement each other for a job well done.
Meta-game wise, playing several rounds together can also transform a group of players who don't know each other (and aren't Griefers) into a (temporary) Band of Brothers.
Furthermore, the game encourages players to assist one another by various methods:
On most servers, you can earn points by assisting in a kill, putting out a burning teammate, and unleashing an Ubercharge in addition to killing enemies and achieving map objectives.
Most of the Medic's achievements are accomplished by helping other classes. One even involves healing someone while they get an achievement.
The Soldier can earn an achievement for using the Buff Banner on his Steam friends called "Banner of Brothers". (The Spy, on the other hand, gets an achievement for backstabbinghis Steam friends...)
The Engineer recently acquired a set of his own achievements, a significant portion of which involve co-operating with other Engineers for the greater good of his team.
In MMORPGs a guild of players can easily approach a version of this. Although you will never actually meet them in real life, you become emotionally attached to those people and are willing to go out of your way to help them in-game and even outside the game. When one of them leaves the guild, it feels like a betrayal.
In Baten Kaitos: Origins, this features heavily in a literal and figurative sense. Every time one of the monsters is defeated, Sagi gets a faint-inducing headache, and wakes up in a different world. in this world, he is a sibling of the five people who group together and become Malpercio, the Big Bad of the sequal.
Illustrated in Left 4 Dead 2. When the game starts out, Four strangers have gathered on the roof of a savannah hotel just as the last evac copter flies off. Five levels later, they are bound by blood, bile, and a few other unrecognizable fluids.
Also in the Sacrifice Comic, when it looks like our heroes are done for, Louis announces "I love you guys". Then Bill Runs off to restart the generator and shouts, "Take care of each other, you guys are the only family I've got left!" Bill's dying lines in the video game have a similar effect.
According to Alistair in Dragon Age: Origins, Grey Wardens of Ferelden were one of these. Depending on the player choices the Grey Wardens of Amaranthine can bond and become close friends as well.
The Horde in World of Warcraft is an example. It's been described as a closely knit family, and an alliance of convenience, and they have had their share of betrayals and mistrust, but the different races of the Horde always have each others backs, and have never denied each other aid when they truly needed it.
The Foxhound unit from the Metal Gear Solid fancomic The Last Days of Foxhound is a highly dysfunctional covert ops group that, in the earlier parts of the comic, all more or less hated each other. (Particularly with members Psycho Mantis and Revolver Ocelot, who do everything from exchanging put-downs to fighting deathmatches, and in one case Mantis only avoids being poisoned by Ocelot by sheer luck.) Of course, later on the group (well, aside from Mantis and Ocelot) does seem to be getting closer to each other to the point that the entire group risks causing, (or at least not preventing) an international incident just to save Sniper Wolf.
And when Liquid discusses the idea with the ghost of the Sorrow, the latter mentions how the Cobra unit were closer than family, with them all considering the Boss to be a mother figure, in spite of her being the youngest of them. This leaves Liquid slightly squicked out as he notes the fact that the Sorrow and the Boss were lovers.
In The Order of the Stick, the rest of the team saves Belkar from being killed by Miko, even though they hate him. Yes, they hate Belkar, but they hate Miko more, and Belkar's still a member of their team. They also keep him in the group to lessen the amount of damage he can do.
The exact words Vaarsuvius said when saving Belkar from Miko were, "Belkar is a horrible, loathsome, supremely selfish creature who behaves contemptibly, laughs at the pain of others, has no manners whatsoever, and whose mental acuity would be compared unfavorably to that of a table. And yet I find I still prefer him to you."
Also when Elan gets captured, they all go to rescue him, even though his stupidity has gotten them in trouble often. Roy at first refuses to but then realizes how horrible it would be to abandon Elan. It's later mentioned that if he hadn't changed his mind, he would have gone straight from Lawful Good to True Neutral. Note that this decision wasn't so much based around the concept of a Band of Brothers, but Roy realizing that Elan is an innocent and the kind of person he should be trying to protect, even if he is annoying.
Belkar hates his companions as much as they hate him. But does he even slow down when it comes to killing lots of people in order to save Haley from execution? Of course not...
The Global Guardians, the superhero team that gives the Global Guardians PBEM Universe its name, started out one of these, but became even moreso after the events of the the September 11th, 2001 terror attacks in which they lost one of their own while rescuing people from the collapsing World Trade Center.
Team Kimba of the Whateley Universe, who have had each other's backs since the first team story "Quoth the Ninja Nevermore".
The eponymous Able Squad in Exo Squad is basically a Band of Brothers, especially for characters like Nara Burns, who was orphaned by the war.
Martian Manhunter feels this way about his fellow Justice League members.
Raven, the loner, is the first to call the Teen Titans her family. Five teenaged orphans living together is justified. Robin and Starfire complicate this somewhat, however, showing romantic feeling for each through all five seasons and ultimately becoming a couple in Teen Titans: Trouble in Tokyo.
The main crew of Transformers Animated (plus Sari) is like this. Optimus even refers to it as "this family" in season 3.
Arcee refers to her team as family in the first episode of Transformers Prime. In season three, Optimus has to explain this to straight-laced Ultra Magnus - they're not the Elite Guard, and have grown into something greater than an army.
Magnus: Optimus. When we spoke earlier - what could be greater than an army?
Optimus: A human concept. One I have learned since coming to Earth: family.
Graveheart from Shadow Raiders gives a rousing speach before the assembled forces of The Allaince before their battle against planet Remora, the Beast Planets envoy, including the iconic 'Band of Brothers' line from Henry V.
Ice-Hockey teams. Hurt one player, especially the goalie, and on ice team mates will come after you.
To varying degrees this is true for almost any sports team, it's just that hockey allows them to show it more violently.
To several Pre-Columbian Native American cultures, being a blood brother to another man meant being his brother not in the sense of family, but rather being the one man above all others that could be counted on to be there when the going got rough.
During the Battle of the Nile, Admiral Nelson explicitly referred to his sea captains as a Band of Brothers, and when once asked what he meant by the phrase, he explained that they were a brotherhood forged together in seamanship and blood.
Easy Company, 506th Parachute Infantry Regiment (pictured above), as described in the book and miniseriesBand of Brothers, is one of the better known examples.
Private Kurt Gabel, 513th Parachute Infantry Regiment, quoted in the book Band of Brothers...
The three of us became an entity. There were many such entities in our close-knit organization. Groups of threes and fours, usually from the same squads or sections, core elements within the families that were the small units, were readily recognized as entities. Often three such entities would make up a squad, with incredible results in combat. They would literally insist on going hungry for one another, freezing for one another, dying for one another.
Semper Fidelis Motto of the U.S. Marine Corps and a few other Organizations around the world. Meaning Always Faithful
Not only that, but the military unit is often analogized as a family, with the commanding officer filling the role of a traditional father or head of the household, and the senior NCO as the mother. The rest of the unit, of course, is like their numerous children, brothers and sisters who sometimes bicker amongst each other, but trust in one another like a family.
Evan Wright's book Generation Kill, an account of the USMC's First Force Recon in the 2003 invasion of Iraq, showed a rather striking scene where a group of Marines were under heavy fire in a field, and were laughing and joking. When asked why they were in such a good mood, the answer was that the Marines were surrounded by their closest friends and combat brothers; if they died in combat, they would die right alongside their best friends.
The HBO adaptation of Generation Kill has an interesting subversion. The Marines are every bit the Band of Brothers you'd expect them to be, but they also quickly adopt their embedded reporter, Evan Wright, as one of their own instead of turning him into a Butt Monkey. In the novel (discussed below), Wright is self-conscious of this process in a way that might pass for Casual Danger Dialog, noting that he realized the Marines were starting to like him when they began poking him with their combat knives, among other forms of hazing.
Throw dart in a Military base in Afghanistan, you'll find one. Whether it be the Mercian Regiment joking about the tracks on their APCs in Camp Bastion, or the Marines trekking it through sandy streets in Sangin, or even a Danish company trading jokes about their duties, the ISAF forces are made of these.
Also commonly invoked and discussed with police officers and firefighters. Entire precincts and fire stations are known to help each other in times of grief and need.
The Wehrmacht. Founded in 1935, it had abolished the old adage that "a soldier should fear his sergeant more than the enemy," which was the bread and butter of the Prussian military, and instead built heavily on the esprit du corps. Units went together through basic training with their officers, soldiers were recruited from the same general area and were kept together through the fighting.
The Israel Defense Force inculcates a culture of referring to one's compatriots quite literally as "brother", and comes complete with No One Gets Left Behind.
Older Than Feudalism: The hoplite phalanx worked like this. The first row of hoplites would stand in formation such that their shields overlapped slightly, so each individual soldier was not only protecting himself, but the soldier to his immediate left. Hoplites were literally taking care of each other in battle. This is why coming back from battle without a shield was such a serious condemnation for a soldier. A hoplite shield was so heavy, that someone running from battle would have to leave it behind...which was the only conceivable reason to come back from battle without it. If you didn't have your shield, you couldn't protect the guy next to you. If you consciously threw away your shield, you were effectively refusing to protect a fellow soldier...which is even worse than simply refusing to fight.