Julius Caesar is the most powerful general in Rome, celebrated by the people on the day of the triumph and feared by Romans who think he may accept the crown. In the play, he is killed by the conspirators on the Ides of March.
On stage, he appears only a few times and speaks of himself by his own name. At the Lupercal (Act I, scene 2), he orders Calpurnia to stand in Antony's path, dismisses the soothsayer as a dreamer, points to Cassius as dangerous because he thinks too much, and says that he is always Caesar. He asks Antony to stand on his right, because that ear is deaf, and Casca reports that he fell in the square and foamed at the mouth.
On the morning of the Ides (Act II, scene 2), he resists Calpurnia, who cried out in her dream that they were killing him, and the omens, which found no heart in the sacrificed animal. He says that "the coward dies a thousand times before death" and yields to his wife's request, until Decius reinterprets the dream, says that the Senate will give him a crown that day, and that the senators will mock him for being afraid. In Act III, scene 1, he does not read Artemidorus's letter, refuses Metellus Cimber's petition by saying he is as constant as the North Star, and falls under the daggers.
The Caesar described here is the character Shakespeare built for the stage, and not a portrait of the historical man.