Success is counted sweetest — Flea War

Success is counted sweetest 1
By those who ne'er succeed.
To comprehend a nectar
Requires sorest need.

Not one of all the purple Host 5
Who took the Flag today
Can tell the definition
So clear of Victory

As he defeated-dying-9
On whose forbidden ear
The distant strains of triumph
Burst agonized and clear!
(F.112/J.67)
[1] Success:: winning a war in the battlefield of a dog's body.
[2] those:: fleas that lose the battle.
[3] nectar:: the blood.
[4] sorest need:: the need of blood; a hint on the effect of flea's bites.
[5] purple Host:: a host of fleas of a dark color.
[6] Flag:: the tail of a setter or Newfoundland dog (OED n.4 4). Dickinson had a dog Carlo, the only one in her life.
[7, 8] definition, Victory:: a flea needs no definition of victory; it just bites.
[9] he, dying:: the failed, exhausted flea (that can't bite anymore).
[10] forbidden ear:: the dog's ear, sweet to flea as the forbidden fruit to human.
[11] strains:: strong muscle reactions due to the bites of the flea in the tail. distant:: far off for a flea from tail to ear.

'puke color' is apparently puce color, and which is now generally understood to be a dark purple: it is a little inclining to red.—flea-color. ─ Shakspeare's Himself Again (1815)

"Your Majesty's gown is very like the colour of fleas!" This sagacious remark was buzzed abroad, until every lady in the land became fidgety, until she had dressed herself in a silk gown of a flea colour. The rage was caught by the men, and the dyers worked night and day, without being able to supply the demand for a flea colour. They nicely distinguished between an old and a young flea ─ The History of the Life and Reign of William the Fourth (1837)