Karna,after he was disowned by Kunti Devi, was brought up by a childless charioteer named Adhiratha and his wife Radha (Karna was called Radheya in his early days).
But Karna was not prepared to take up the profession of a charioteer .So he went to the revered sage Parasurama and learnt archery pretending to be a Brahmin. But when Parasurama found out that he was not a brahmin but the son of a charioteer, he cursed Karna to forget the Brahmastra(a powerful invocation) in his hour of need.
When he was returning home after his tutelage with Parasurama,Karna heard that the Pandava princes were showing of their prowess in warcraft at Hastinapura.Karna at once set forth to Hastinapura.And having reached there,he repeated with ease all the feats that Arjuna had performed with the bow.He then challenged Arjuna to a duel.But in the olden days,duels could be held only between equals.To solve this predicament , Duryodhana chivarlously made Karna,the King of Anga.Unfortunately,the sun had set and their duel had to be postponed to a more fateful day.Nevertheless,Karna became a staunch friend of Duryodhana from that day onwards.(Karna is very much like the Hector of Illiad).
Meanwhile,the Pandavas and Kauravas were at first trained by Kripa and then as they grew older by Drona,a renowned practitioner of war craft.Drona was an unrivaled archer in those days.