What is young fortinbras like? Why has he chosen this time to attack? act 1

Young Fortinbras is a "hothead" who is always ready for a war. He is the nephew to Old Norway. He is angry that his father was killed in the war with Denmark and that they lost land. He wants the land back. Now that Hamlet Sr. is dead, he thinks Denmark is in a vilnerable state and weak. He thinks thisa is a good time to attack them.