Dante Alighieri was born in the city-state of Florence in 1265, sometime, according to his Vita Nova, under the sign of Gemini. Born to a family of little note and wealth, he is now considered one of the greatest poets in the Italian language, and he forms the classic trio of Italian authors along with the comic story-teller Boccaccio and the poet Petrarch. Much of our knowledge of him comes from his Vita Nova, in which he recounts his life as it relates to his tragic love for Beatrice, who features prominently in much of his work. He first saw Beatrice when he was almost nine years old and she was some months younger. Beatrice went on to marry another man, Simone di' Bardi, who was a well-connected and wealthy Florentine figure. She died when Dante was 25, such that their relationship existed almost entirely in Dante's imagination. Nonetheless, she plays an extremely important role in his poetry. Dante attributed all the heavenly virtues to her soul and imagined, in his masterpiece The Divine Comedy, that she was his guardian angel who alternately berated and encouraged him on his search for salvation.
Politics deeply influenced Dante's literary and emotional life. Renaissance Florence was a thriving, but not a peaceful city: different opposing factions continually struggled for dominance there. The Guelfs and the Ghibellines were the two major factions. Their civil strife had effects in Italy as well as other countries, as it concerned not only local politics but papal and imperial conflicts. The pope and the Holy Roman Emperor were political rivals for much of this time period, and in general, the Guelfs were in favor of the pope, while the Ghibellines supported Imperial power. Yet, beyond these large-scale disputes, the Guelf-Ghibelline conflict was often complicated by a series of local divisions and rivalries, causing near-constant violence on a local level not directly conditioned by large-scale political concerns. These turbulent conditions and complex disagreements made it such that, ultimately, cycles of vengeance and unjust persecution seem to have defined much of Florentine public life.
By 1289, after the battle of Campaldino, the Ghibellines had largely disappeared from Florence. Dante himself fought for the Guelfs at Campaldino; his experiences in the battle are subtly alluded to in the Purgatorio. Italian peace, however, did not ensue. Instead, the Guelf party divided between the Whites and the Blacks (Dante was a White Guelf). The Whites were more opposed to papal power than the Blacks, and tended to favor the emperor, so in fact the preoccupations of the White Guelfs were much like those of the defeated Ghibellines. In this divisive atmosphere, Dante rose to a position of leadership. In 1302, while he was in Rome on a diplomatic mission to the pope, the Blacks in Florence seized power with the help of the French (and pro-Pope) Charles of Valois. The Blacks exiled Dante, without his family, confiscating his goods and condemning him to be burned if he should return to Florence. It is believed that he did not see his wife again.
Dante never returned to Florence. He wandered from city to city, depending on noble patrons for financial support. Dante's struggles during this period of exile are alluded to by Cacciaguida in the Paradiso. Between 1302 and 1304 some attempts were made by the exiled Whites to retrieve their position in Florence, but none of these succeeded. Dante contented himself with hoping for the appearance of a new powerful Holy Roman Emperor who would unite the country and banish strife. Henry VII was elected emperor in 1308, and indeed laid siege to Florence in 1312, but was defeated. He died a year later, destroying Dante's hopes. Dante passed from court to court, writing passionate political and moral epistles and finishing his Divine Comedy, which contains the Inferno, Purgatorio, and Paradiso. He finally died in Ravenna in 1321.
As can be seen, little is known about the details of Dante's life other than what he tells us in his works and his representation in the work of Boccaccio. A portrait emerges of a bitter and passionate man who, once distanced from politics, came to use his prophetic poetry to warn Florentines of the evils which awaited them for their misdeeds and the confusion and corruption of their government.
Notably, he was one of the first authors to write in the vernacular Tuscan, rather than Latin, and thus had a defining effect on what Italian is today: before his work, Italian was usually only spoken, and hence was divided into many different dialects, without a coherent literary language. Dante used the melodic vowel word-endings of many Italian words in the rhyme scheme terza rime, in which the first and the third lines of each triplet end in the same vowel sound. The success of his Commedia came to define and influence the propagation of vulgar poetry (so-called because it used the common or "vulgar" language) throughout Europe.