Horatio and Marcellus see the ghost as the harbinger of the dark times coming for Denmark. Horatio connects the warlike appearance of the spirit to the armed conflict with Norway.
In Act 1, Horatio, a close friend of Hamlet, joins the guards on their night shift at the royal palace. He wishes to see the ghost Marcellus told him about. Firstly, Horatio is skeptical about the experience. However, he is “harrowed with fear and wonder” when it appears. He attempts speaking to the ghost, but without success. When it disappears, Marcellus and Horatio discuss the current state of affairs in Denmark.
Horatio speculates that the military’s recent activity has to do with the Norwegian prince preparing for a war against Denmark. He reminds the guards that the old king of Denmark conquered Norwegian lands and killed their king. That is why Old Hamlet presumably visited them in the ghost form. Besides, Horatio compares him to Julius Caesar. He refers to the violent unrest, which followed the latter’s assassination.
Horatio’s speech is interrupted by the ghost briefly reappearing and then vanishing with the rooster crow’s sound. As Lewis states:
“The Ghost is in pursuit of something — be it revenge, Hamlet, or the Norwegians against whom Francisco, Marcellus, Barnardo, and Horatio are standing guard.”
Horatio proceeds to tell Hamlet about the ghost, assuming it will speak only to him.