What three things does Wheatley compare the Colonial Army to in her poem "To His Excellency General Washington"?

In Phillis Wheatley's famous poem in praise of George
Washington "To his Excellency George Washington," Wheatley uses a neoclassical style
with classical allusions (e.g., "The goddess comes, she moves divinely fair, / Olive and
laurel bind her golden hair") to describe Washington leading the nation in war. While
America is "Columbia" (e.g., "When Gallic powers Columbia’s fury found"), Washington's
army is metaphorically compared to a "warrior's train" (line 20), a "martial band" (line
26), and "Columbia's arm" (line 34).

The comparative
metaphor of a warrior's train brings up images of Medieval warriors fighting for truth
and righteousness arrayed in ranks and rows behind the valiant Lord or Knight or
Sovereign King leading them forward. A "train" in this sense is the military formation
of troops in rank and file. Washington's "martial band" is a military allusion to a
united group dedicated to one purpose (i.e., band), while "martial" refers to that which
is associated with armed forces.

In calling America " title="Columbia: Word Origin & History. Online Etymology Dictionary. Douglas
harper 2010. Dictionary.com"
href="http://dictionary.reference.com/browse/columbia">Columbia," Wheatley
echoes the female name for the United States that alludes to the name of Christopher
Columbus and that was used for the British American colonies as early as 1730 (Online
Etymology Dictionary at Dictionary.com). So "Columbia's arm" signifies the military
strength and power of the nation of the United States.