Drona was the son of Rishi Bharadwaj.He and prince Drupada of Panchala country learnt from Rishi Bharadwaj in Gurukula(Vedic school conducted in olden days in an Ashram where children from various places stayed together & taken care of by the ashram Rishi & his wife including there food).Drona & Drupada became friends.Drupada promised Drona that he would help him when he becomes the king.Later Drona got married & a boy was born to him.But they became so poor that he found it difficult to feed his child.At least if he had a cow ,he can feed his child with cow's milk .Earlier during their studying period in Gurukula,Drupada has promised to give him half his kingdom.Remembering this he went to Panchala country where now Drupada has become the king.After the soldiers told king Drupada that a poor Brahmin is waiting to see him,who says that he is your friend, Drupada asked the soldiers to let him in. During the same period, Krishna was learning from Sandeepani Rishi in a gurukula.There he met a brahmin boy Sudhama who became his close friend.After the studies they parted.Later Krishna became the king of Dwaraka.Meanwhile Sudhama got married &got several children.They became very poor. Sudhama's wife came to know that Krishna was a close friend of Sudhama & he was the king of Dwaraka.So she asked his husband to seek the help of his friend Krishna who was a king then.Sudhama felt very shy to ask his friend Krishna any help & after lot of persuasion from his wife ,he agreed to meet his friend Krishna to seek help.He took a handful of rice flakes in an old cotton bag which is a favourite food of Krishna.After a long journey he approached the guards in the entrance of Dwaraka palace.He was wearing an old dhoti.Guards were surprised to learn that he was a friend of their King.They informed Krishna about Sudhama .Krishna immediately rushed to Sudhama leaving his important kingly activities.He met Sudhama at the entrance & hugged him ,took him inside his palace .He introduced him to his wife Rukmani.He asked his servants to take care of him very well.He searched Sudhama &grabbed the old cotton bag,ate his favourite rice flakes,while sudhama felt very shy as he could not bring any sweets & costly gifts to his friend.Rukmani was also surprised to see Krishna happily eating rice flakes. In panchala palace,Drupada asked Drona why he came there. Drona told him that he got married& having a son &told about his poor condition.He reminded Drupada about their studies in Gurukula & his promise of giving him half of his kingdom.He asked him just a cow to feed his child & not his land.Drupada laughed at him & replied that friends should be equal in status & how a poor man like Drona & a King like him be friends.He sent him back empty handed even though he could have helped him taking into account the promise he gave to his friend during their studies.He also ridiculed him & told him that if he came next time to meet him, he would be driven away.Drona returned home empty handed.He took his wife & son to Hatinapur in search of a job.There Pandavas & Guaravas(princes) were playing outside the palace.There wooden ball fell into a well nearby.They were hopelessly looking at the well to retrieve the ball.Drona saw this ,took back the ball with arrows from a bow.Princes were over joyed at this & told their grand father Bheeshma about this.Bheeshma as an expert in bow & arrow applications,found the talent in Drona &Immediately appointed him as his grand children's Teacher to teach them Dhanur Vidya.He was given a good home & all other facilities.So Drona became comfortable & his family was happy. After few days of his staying at Dwaraka ,Sudhama told his friend Krishna that he was returning to his native where their family would be waiting for him.He felt shy & did n't ask his friend any help.Rukmani asked Krishna the direction at which Sudhama's house was located & looked at that direction.Sudhama returned to his village.He was surprised to see lot of well built bungalows & neat roads rich people roaming there in his village.He reached his house where a well built modern bungalow was there.He saw a rich lady wearing gold jewels coming out of his house & kneeling before him in respect.To his surprise that was his wife.His children were playing wearing costly dresses.Then only he remembered his friend Krishna & His Wife Rukmani(Goddess of wealth).The Whole village praised Sudhama & told him that because of him & Krishna only they all have have become rich.Sudhama & his wife were in tears thinking of Krishna. Drona taught Pandava & Guarava princes Dhanur Vidya very well.After completion of the training ,students they have to offer Gurudhaksina ,a honorarium (gift containing money & other articles) to their teacher.Arjuna ,the Pandava prince became the favourite student of Drona & learnt all the war techniques .When he tried to offer Gurudhakshina his teacher Drona requested Bheeshma to send Arjuna with him. They went to Panchala & on the way told Arjuna,how he he was humiliated by king of Panchala &asked Arjuna to defeat him in a war with his teachings.Arjuna obeyed his Guru & defeated Drupada in the war & he was tied in a chariot & taken to Hatinapur as a slave of Drona.Now Drona instructed his old friend to part with half of his kingdom.So there is no other way for Drupada except to part with his kingdom.He was humiliated.