Casual Shakespeare readers may know Fortinbras as the minor war-hawk character from Hamlet who wants his father's land back after Hamlet's father defeated him in battle and claimed it for Denmark. He's cunning, ambitious, and utterly determined.
Indeed, his name means 'strong of arm', very significant for the character of Fortinbras. You see, Old Norway's nephew is not simply a plot device invented by Shakespeare to come through and clean things up after Hamlet's tragic and timeless death. And despite the tendency of filmakers to nearly universally cut his part first for performance, he plays a vital role in defining the greater significance of Hamlet's psychology.
This particular play relies heavily on foils, and Fortinbras is a foil for Hamlet, in addition to Laertes and Claudius. And as any good foil, he is integral to providing comparison and contrast for the entirety of Hamlet's chracter, which is arguably considered in general to be one plagued by indecision. And wherever Hamlet is irresolute, Fortinbras is 'strong of arm'.
Consider their respective positions. Hamlet has lost his father; Fortinbras has lost his father. Hamlet seeks vengeance; Fortinbras seeks vengeance. The difference? Hamlet whines, bemoans his existence, sulks, sneaks. Fortinbras cleverly and swiftly invades Denmark, reclaiming his father's lands and restoring order. When Hamlet witnesses him leading an army to Poland, he laments
“Witness this army of such mass and charge, / Led by a delicate and tender prince, / Whose spirit, with divine ambition puffed, / Makes mouths at the invisible event, / Exposing what is mortal and unsure / To all that fortune, death, and danger dare / Even for an eggshell…” (4.4.47-53).
Fortinbras is a leader with clear ambition
s, Hamlet, is paralyzed by his madness.
And as the restorer of order, Fortinbras does what Hamlet could never do. And perhaps most significantly, Fortinbras acts decisively and lives whereas Hamlet's fiasco results in a divided kingdom, and his own death in addition to the death of many others. In some ways, this makes Fortinbras the incarnation of a critique of Hamlet's tragic flaw.