in Act I, Sc. II of "Hamlet," how does Claudius react to the threat of Fortinbras?
In the first act of Hamlet, King Claudius learns that Prince Fortinbras of Norway is enraged after learning that King Hamlet killed his father. He is gathering troops and planning to attack Denmark in retaliation for the death of his father.
In Act I Scene 2, Claudius informs Polonius, his son Laertes, Queen Gertrude, and Voltemand and Cornelius that Fortinbras, son of King Fortinbras, who has died, threatens to invade Denmark in order to retaliate for the death of his father. He wants also to reclaim the land taken from Norway:
He hath not failed to pester us with messageImporting the surrender of those landsLost by his father, with all bonds of law... (I.2.23-25)
In order to avert this threat, King Claudius is sending Voltemand and Cornelius to Denmark. There the two men will try to contribute to the well-being of Denmark by convincing the old uncle of Fortinbras to keep his nephew in the country--"to supress" his nephew in his purpose. In other words, Voltemand and Cornelius must prevent conflict between Norway and Denmark.
Claudius directs Cornelius and Voltemand to deliver a message to Old Norway about his nephew Fortinbras' aggressive actions. The old man, sick and bedridden, knows nothing of Fortinbras' plans. Claudius hopes that the Danish messengers will alert Old Norway so that he can now control his nephew and eliminate the threat to Denmark.
Claudius' action here in response to the threat reveals his awareness of current events as well as his expertise--and possible experience--in handling what could result in war if left unattended. He wants to impress the Danish court in this scene that he is a competent monarch worthy of their respect.
Claudius, in contrast to King Hamlet, is more a "lover than a fighter." King Hamlet was a warrior king who probably would have gone to war against Norway. Claudius, however, sends two ambassadors to Norway, Voltemand and Corneliius, to negotiate with Norway's king. They meet with success as Old Norway reins in Fortinbras by paying him money not to attack Denmark but, instead, to wage war against Poland.