The Three Musketeers begins with a young Gascon, d'Artagnan, leaving his home in the provinces of France to make his fortune in Paris. His father gives him, as parting gifts, an old yellow horse and a letter of introduction to Monsieur de Treville, head of the King's Musketeers, the elite group of soldiers who make up the King and Queen's personal bodyguard. D'Artagnan's father advises him to be guided by his courage and his wits, to take no flack from anyone but the Cardinal and the King, and to remember that with bravery and determination he can achieve anything. D'Artagnan's mother gives him the recipe for an herbal salve that will heal any wound he sustains in battle very quickly, and with that the young man leaves home to make his fortune.
At his first stop, in the town of Meung, the hot-headed d'Artagnan gets into a fight with a distinguished-looking gentlemen who ridicules him because of his mount. D'Artagnan is beaten unconscious by a group of the gentleman's lackeys. When he comes to, he sees the gentleman talking to a beautiful, fair woman in a carriage whom he calls "Milady," just as the two of them are riding off. He prepares himself to leave the town, but finds that the gentleman has stolen his letter of introduction to M. de Treville.
Disheartened by the loss of the letter, but nonetheless full of Gascon spirit, d'Artagnan rides on to Paris and finds the home of M. de Treville. Here, he is cowed by the profusion of Musketeers who spend their days lolling about de Treville's house and courtyard, telling stories of amorous and military conquests, and mocking the Cardinal (to d'Artagnan's shock). D'Artagnan is received into M. de Treville's private chamber. However, before the two can speak, de Treville calls in two of his musketeers, Aramis and Porthos. Aramis is a slight, somewhat foppish young man whom d'Artagnan had just overheard describing his intentions to eventually leave the Musketeers and enter the Church. Porthos is a loud, proud, Saint Bernard-like fellow who d'Artagnan had just witnessed showing off his new sash.
M. de Treville upbraids these two men, and their companion, the absent Athos, for a recent skirmish with the Cardinal's guards in which they were defeated and arrested, calling them cowards. The men defend themselves, noting that they did in fact kill a couple of the guards. Then, Athos--a handsome, highly distinguished man, the oldest of the three friends--makes a dramatic entrance, clearly overwhelmed by the pain of his wound. M. de Treville is mollified by all of this, and his attitude turns from scolding to fatherly. But before he can praise the men Athos collapses from his wounds, and the whole household erupts into a fervor, looking for a doctor.
After Athos has been tended to and everything has cleared up, d'Artagnan and M. de Treville resume their interview. D'Artagnan explains the story of how he lost the letter, which, on top of a shared Gascon heritage, sparks the great man's interest in the young d'Artagnan. However, de Treville suspects that d'Artagnan might be an agent of the Cardinal, so he tests him by praising the Cardinal, guessing that any agent would have been trained to joke about the idiocy of the "Red Duke." D'Artagnan surprises de Treville by eagerly agreeing, and saying how shocked he was at the Musketeers' insults to one of France's most powerful men. However, before the interview can continue, d'Artagnan spots the Man from Meung, and goes tearing out of the house to challenge him.
The most dominating fixture of this first portion of The Three Musketeers is our hero himself, the young d'Artagnan. Dumas emphasizes a certain "Gascon hot-headedness" that the hero seems to possess. D'Artagnan is proud--he comes from a noble background, but he is a provincial, and is thus uncultured in the ways of the Court and politics. He is also very, very poor. Dumas paints, initially, a somewhat comic portrayal of the young man as a proud, insecure swaggerer who seems prone to interpret every look as an insult, and every insult as an invitation to a duel. This is what gets him into a fight with the fellow in Meung. We will see, as the story progresses, other very important character features emerge from d'Artagnan, but for this first portion and a bit afterwards, his penchant for feeling his honor insulted dominates the scene.
Why does Dumas choose a provincial, a Gascon, as the center of his story of political intrigue and adventure in Paris? For a nation reeling from the turmoil of the French Revolution, a character from far away from Paris--the seat of the political upheaval--was least likely to become associated in his readers' minds with revolutionary ideas and factions, and therefore best able to convey a sense of unified national character. Further, Dumas himself moved to Paris from the provinces to seek his fortune. Finally, d'Artagnan's aura of freshness and idealism is in many ways dependent on his role as an outsider; he has not been corrupted by city life, and is alien to its cynicism. D'Artagnan is a Romantic hero in a historical context.
In this first section of his story, Dumas wastes no time setting up what is going to be the fundamental political rivalry of The Three Musketeers, the one that will drive the story. This rivalry is between King Louis XIII and Cardinal Richelieu, nominally the King's most trusted advisor. As Dumas presents things, this is the situation: France is divided between Royalists, who support the King, and Cardinalists, who support Richelieu. Richelieu is the more powerful of the two men--he is far more intelligent, and his network of influence is greater. The King's primary pull is the fact that he is the King-- he represents the monarchy and, therefore, the history and values of France. What Dumas presents here is a clear division between these two factions, and a clear statement that the Musketeers represent a stronghold of Royalist sentiment. Every conflict in the story is couched in these terms- from d'Artagnan's very first encounter of the book, with the Man from Meung--a Cardinalist agent.
In terms of historical accuracy, Dumas presentation of his setting is more or less reliable. The historical tradition does indeed remember Louis XIII as a somewhat insipid ruler, and Richelieu was the dominant figure of the age. And there did exist a split within the government; the King had his followers, and the Cardinal his. The two men were not in open conflict--indeed, the King bowed to the Cardinal in most things--but their followers often were, particularly the King's Musketeers and the Cardinal's Guards, just as Dumas indicates.