How is tension and suspense created in act1 scene1 of Hamlet

Tension and suspense are created from the very beginning
of the play.  The first act and scene features a midnight watch in the bitter cold. 
They are joined by Horatio, a close friend of the title character Hamlet, and hope that
he can help them sort out a strange, ghostly occurrence.  It seems that the ghost of the
recently deceased King, Hamlet's father, has been appearing at night, dressed in his
army as if ready for a fight.  This has frightened the watchmen and does thes same to
Horatio, as noted by one of the guards, Bernardo:

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How now, Horatio! you tremble and look pale:

Is not this something more than
fantasy?

Beyond the
appearance of the dead king, Horatio relates a bitter rivalry between their home,
Denmark, and neighboring Norway.  With a dead king, an attack may be imminent.  In
addition, Horatio compares this evening to the night of Julius Caesar's death when the
dead rose from their graves and likens it to foreboding
doom.

A little
ere the mightiest Julius fell,
The graves stood tenantless and the sheeted
dead
Did squeak and gibber in the Roman streets:
As stars with
trains of fire and dews of blood,
Disasters in the
sun;

All of these things
raise the level of suspense and tension in the reader.