Who is considered a soldier?

As the play begins, it is nighttime and very cold, and two named characters (Bernardo and Francisco) and two unnamed sentinels are on watch on a platform of the castle of Elsinore, Denmark. Francisco, who was just relieved by Bernardo exits after speaking only a few lines. We never see him again in the play.

Strangely and ironically, the only other single soldier referred to in the play is Hamlet, who is not really a soldier. So we have Francisco on the first page of the play and dead Hamlet on the very last page, and the very last lines of the play, soldiers both.

FORTINBRAS:

Let four captains

Bear Hamlet like a soldier to the stage;

For he was likely, had he been put on,

To have proved most royal; and, for his passage,

The soldiers' music and the rites of war

Speak loudly for him.

Take up the bodies. Such a sight as this

Becomes the field, but here shows much amiss.

Go, bid the soldiers shoot.

Fortinbras sees Hamlet as a soldier, for Hamlet fought valiantly against his own nature and for the soul of his suffering father.