The fighter class can basically be described as the most common of the adventuring classes. Whether this relates to all NPCs within your game world or taking into account your various PC groups. Considering that almost all soldiers, city guardsmen, and hired men-at-arms are of the fighter class. Therefore, even if not one of your players have ever played a fighter, they would still be the most numerous type of characters in any world. Many players have simply decided to become a fighter and thus roll up his stats. Placing the higher numbers in Strength, and Constitution. So other then writing 'fighter' on your character sheet, under 'class', lets discuss what caused your PC to have sword in hand.

First, there is the need within the game's structure to have at least one good fighter. For a party of thieves or mages would soon find themselves dead shortly after leaving a city setting, without the strengths and hit points of a 'protecting' fighter. Although this position can be filled with that of a Paladin, Ranger, or Barbarian, these tend to restrict the actions of a character. And even if they can be fun to play, the very nature of these classes dictate much of your role-playing choices.

Secondly, as most start the game in the lower levels, more often even first level, these are the most survivable. With a good selection of skills and feats the fighter class is fully capable of handling himself at a very low level. This can not be said for the other two primary classes, thieves and mages. Both of which must wait until mid-level to shine. So a player who wants a lot of action early, without worrying too much about being killed to soon, tend to gravitate towards the fighter class.

Now looking outside the context of the game structure, how did he get the training to wield that sword. I'm talking about the character's history. Even to be a first level fighter one doesn't just pick up a sword and start hacking away with it. If this was the case the world would be overran by first level fighters. For even a sharp stick can be used as a spear of sorts. And a spear is just one of many weapons that make up the fighter's combat repertoire. That is why there is a 0 (zero) level under the fighter class. But what takes him to that all important next step...1st Level Fighter. So lets take a look at some of the possible paths a young man might have taken to become this all important fighter.

Military:
The most obvious, and thus the most common, would be a military tour of duty. A call to the banner of the local authority figure. Be it a baron, duke, or king. The endless hours of weapon training and drilling over the course of weeks, months, and even years gives him the needed knowledge to be a fighter. Even if he never actually saw a day of combat or was unable to test his skill against an opponent he would still come forth a first level fighter. With luck behind him, if he did have such encounters with enemy forces and survived then it would be reasonable for him to come into the game at second level. At least first level with some experience points already under his belt. Therefore, if a player tells you that a military background is where his PC learned the use of his sword, I would consider that, as a DM, reason to give such an advantage.

Father to son:
Then there's the father-son training. Perhaps his father was a military veteran and wish to raise his son as a warrior. Most often this happens in militant societies. You also have those that live on the frontier and the training of ones offspring is necessary for their survival. Practical experience occurs during the number of raids from the local natives or enemy border patrols. In either case the saying goes, 'born with a sword in hand'.

The first two previous backgrounds would be the most common source of pumping out the needed fighters of any world. Even military or father-trained fighters can use this type of history to enrich their role-playing. Whether its having contact within the army or city guard, or being burdened by or carrying on the legacy of one's 'old man'. As for fighters, these two are the most common, world wide, what other ones are possible? For, although to have such a background is not something to be taken lightly, it can be boring character after character.

Training Centers/Warrior's Guild:
Many worlds have set up public training camps. Thereby young men without apprenticeship in a worthwhile trade can find work as men-at-arms. Guarding the caravans of overland trade routes, hiring themselves out as bodyguards to the wealthy, or massing together as mercenaries. For a nominal fee and finding one's own room and board any one can learn the skills of swordsmanship. In many cases these are the testing grounds for the various fighter oriented brotherhoods, like Mercenary Companies, Guard Unions, and Adventurers Guilds. At times the cost of such training is either reduced or nullified if the trainee officially joins the sponsoring group.
Some of the benefits of having this background, are the camaraderie of fellow brother-in-arms, a multitude of adventuring hooks, and something to do during 'downtime'. 'Downtime', you know, while the mage is off learning new spells from his mentor, the thief is making renewed contact with his own guild, and the cleric is taking in his seminars.

Noble birthright:
A rare one, but still possible. It is after all a fantasy game. As a member of a Noble House, training with weapons is but a part of one's upbringing. The local or royal sword master fulfills your required needs in this area of expertise. For even as with higher schooling and studies of etiquette and chivalry, the use of the sword is a must. The one concern with this background is the fact that the character become a simple fighter.

There are three common reason why such a son of noble birth would not have gone onto better things. Like that of paladin, cavalier, or followed his father, as his heir, a nobleman, or counselor. But instead, became a common adventurer.

First, the loss of face or being disowned. The young man did, or was thought to have done, some act or deed that lead to his stated downfall. A good one for role-playing hooks.

Second, failure to complete or wish to complete the needed training to advance further. Whether this is by either a lack of intelligence or design. Although this could lead to the action of the previously mentioned cause, it does not have to. Some society's rules of conduct allow young nobles to chose their own paths. Perhaps the taking up of great adventuring campaigns is a sign of bravery and heroics. Maybe something the young noble's father did when he was younger, before putting on the mantle of responsibility.

Lastly, it could be the young nobleman's position within the family. As second or third born child he may have been given the same schooling and training but was prevented from advancement. Thus to allow his older sibling to be the family's shining star. Therefore, one of the ways to still create a name for yourself would be to become a 'Hero'.

As you may have noticed this possible character history has been rooted in the concept that the character is male. For although one may have a society that gives equality to women, I see this as extremely rare and hard to swallow in a medieval setting. Young noble women were raised much differently then their male siblings. The lessons they were taught dealt with maintaining a proper household for the nobleman they would marry. Most, actually being kept under tight lock and key to insure their virtuous demeanor. But as with anything there are exceptions. She may be an only child and treated as a son by her father, or she is of a warring clan where all must fight, as they are so few.

Shaped by Events:
This sort of history for a fighter character is based solely on the imagination of the player and/or the DM. The creating of an event or series of events that transforms the character into a fighter can be as much fun as playing him. Of course, luck must play a significant role in the life of the character. To take a common man and change him into a surviving, self taught warrior requires talent in storytelling. The cheapest, and shows the most lacking of such ability, is the concept that the character simply picked up a sword and practiced daily for months, or years, on his own. The story should capture the same awe of that of a Jeremiah Johnson saga. Where a simple man became a legendary mountainman by trial and error, through pain and suffering, and with failure and little success. Until he came forth a true man of the high hills. But, whereas Jeremiah was a mountainman, the character arises a swordsman.

Many of these start with a village raid, the death of a loved one, or being trapped or lost in hostile territory. But keep in mind that a single battle won does not a warrior make. Most of those that I, as a DM, have excepted or created myself took place over many years in the character's life. For not only must he go from lowly carpenter, cargo handler, or farmer to a fighting class warrior, he must also wish to continue his actions as a swordsman. If not, then pray tell why would the player be running him. Although with a little help from the DM this 'farmer-turned-fighter-turned-farmer-again' could be led into taking up his sword once more.

The Natural:
If a player was to say that his character just bought a sword, walked out into the wilderness and killed himself a couple of orcs, I would fall to the floor laughing. The idea of The Natural sounds intriguing, but such hidden talent should come out during events not planned by the character. As in the previous possible history idea, 'Shaped by Events', the character finds his guiding light, not luck but an uncanny sense of skill. This should still not allow the player to skip the awe-inspiring story, just perhaps shorten it a bit. There are naturals in sports (baseball, basketball), learning certain subjects (math, science), and in the arts (painting, writing). But not one of these individuals knew all there is to know about that field when they first started. The true nature of The Natural is the ability to learn that subject's workings very quickly and deduce on their own, how to improve themselves over a shorter amount of time. So the idea of The Natural is usable as a background for a PC, its just taking the place of luck in the events that shaped the character.

Why a Fighter Background?:
I would imagine that over half of the games played are but simple module-using sessions. These take but 3-5 meetings to complete and then the group of players roll up new characters. These they then run through a different module, under a different group member as the DM. This can be a fun way to play the game. It gives each player a chance to be the DM, the players can select and enjoy running different classes within a shorter amount of time, and everybody gets to use those modules they've spent money on. Under these conditions the creating of the character's background would not be of much priority. Other than the couple of minutes of fun in doing so, PC histories has little affect on the playing.

Now if your going to be involved in a DM's major campaign or playing the same character for years then creating a background is a must. It is what defines the character. How he or she sees the world around them. And in such long games it gives the DM a multitude of adventure hooks to use, for and against the characters. A group of gamers can slowly build on their collective histories to add great depth and complexity to the story they are 'living'. It can also be a safety shield for those smart enough to use it. Explaining why your character would do something a certain way, if you can just twist the given history right.

One good reason, not only to have a background, but one that is expansive and, although complex, has elbow room to move about. So take your time, and give yourself time, to create a very workable background for your fighter. For as the fighter you may be looked on as nothing more then the muscle of the group. But with the right history and a player and DM who knows how to use it, it could make that fighter so much more.