Bheeshmaka, the king of Vidarbha had two children, Prince Rukmi and Princess Rukmini. Bheeshmaka had heard many stories of Krishna's valor and secretly wished him to be his son-in-law. He knew that it might not be possible as Kamsa's father in law, Jarasandha, was their overlord and he was Krishna's sworn enemy.
Now Rukmi was a friend of Kamsa and owed his allegiance to Jarasandha. He wanted his younger sister to marry Shishupala, the crown prince of Chedi, who also was favored by Jarasandha.
Rukmini had heard stories of Krishna's valour from her childhood and she had her heart set on marrying him. When she heard that Rukmi had chosen Shishupala for her, she resolved that she would only marry Krishna or die.
She sent for her trusted aid Sunanda, a wise old Brahman. She wrote a note to Krishna telling him that he was the only husband for her and asked if he would come and take her away. She wrote to him, that if he wouldn't have her, she would give up her life. She also begged him that he spare the lives of her family whilst kidnapping her. She wrote that on the day of the wedding, she would go to the temple of the Goddess Parvati (their family deity) and if he would, that was the right time to kidnap her. She sent Sunanda with the note to Dwarka (Krishna's new fortress home).
Krishna had heard a lot about Rukmini's beauty too. He longed to have her but wasn't sure if he should approach her family, as they owed their allegiance to Jarasandha. Upon receiving the message from her, he resolved to kidnap her. Now Jarasandha who knew that Krishna might try something like that to humiliate him, filled Vidarbha with people loyal to him.
Krishna went to Vidarbha first and Balrama followed with the army. On the wedding day, when Rukmini was leaving the temple, she looked in the crowds for Krishna. She did not see him. As she was about to enter her chariot and leave, she felt someone hold her from behind. It was Krishna. He lifted her into the chariot and sped away.
Jarasandha was furious. He rallied all his men and ordered them to chase Krishna. Jarasandha's men followed Krishna but were ambushed by Balrama and his army on the outskirts of the city. Now Rukmi managed to go through Balrama's army and catch up with Krishna and Rukmini. He swore that he would not return to his city without his sister.
Rukmi fired an arrow at Krishna, but it did not even make a dent in Krishna's divine armour. Krishna then fired multiple arrows, which first killed Rukmi's horses and then shattered his chariot. Rukmi then picked up his bow again, but before he could fire, Krishna shot another arrow and shattered Rukmi's bow. Rukmi now mad with rage picked up his sword and ran towards Krishna. Krishna fired another arrow and split Rukmi's sword in two. Krishna then picked up his sword and was about to attack Rukmi when Rukmini begged her lord to spare her brother's life. On Rukmini's saying, Krishna spared Rukmi's life but cut half the hair on his head and half the moustache on his face, the worst insult a warrior could face, and then let him go.
Krishna returned to Dwarka with Rukmini and made her his bride.