What advantage did the spartans have over persians?

They had great physique due to being trained at a young age. They also had great army tactics.

which time period is this? or is this story fictional, i'm going to need more info to answer this question

beowulf is considered an epic poem because it describes the actions of a great warrior.

beowulf is taken into account an epos. in this poem, the main character may be a hero who travels nice distances to prove his strength at not possible odds against supernatural demons and beasts. in the poem, beowulf was a young warrior and he leaves his country to hrothgar, as hrothgar was in a great trouble.