In the poem "Success is counted sweetest," what can a soldier of the "purple Host" not do?

This excellent poem by Emily Dickinson explores and
explains the ironical nature of comprehending success. According to Dickinson, success
is only something that can be fully savoured or understood by, ironically, someone who
does not succeed. Note the way the second and third stanza gives an example to support
this argument by referring to a victorious army, the "purple Host," who wins a battle,
yet cannot understand and comprehend success as much as a "defeated" and "dying" soldier
who lies on the ground, listening to the victory celebrations of his
enemies:

Not
one of all the purple Host

Who took the flag
today

Can tell the
definition

So clear of
Victory

Thus, Dickinson
argues, a victorious army is not able to "tell the definition" of their "Victory" or
understand the nature of their success compared to their defeated enemies. To really
understand success, Dickinson seems to argue, you have to paradoxically not attain
it.