retreat vs pull back

retreat is a noun but pull back is not a noun.

Word	Noun	Adjective	Verb	Adverb
retreat	Yes	No	Yes	No
pull back	No	No	Yes	No

As verbs, retreat and pull back are synonyms defined as:

retreat and pull back: make a retreat from an earlier commitment or activity

Other synonyms of retreat include back away, back out, crawfish, crawfish out, pull in one's horns, withdraw.

As verbs, retreat and pull back are synonyms defined as:

Other synonyms of retreat include draw back, move back, pull away, recede, retire, withdraw.

As verbs, pull back is a hypernym of retreat; that is, pull back is a word with a broader meaning than retreat:

Other hypernyms of retreat include draw back, move back, pull away, recede, retire, retreat, withdraw.

retreat (noun)	pull back (noun)
(military) withdrawal of troops to a more favorable position to escape the enemy's superior forces or after a defeat
withdrawal for prayer and study and meditation
the act of withdrawing or going backward (especially to escape something hazardous or unpleasant)
an area where you can be alone
(military) a bugle call signaling the lowering of the flag at sunset
(military) a signal to begin a withdrawal from a dangerous position
a place of privacy; a place affording peace and quiet

retreat (verb)	pull back (verb)
make a retreat from an earlier commitment or activity	make a retreat from an earlier commitment or activity
pull back or move away or backward	move to a rearward position; pull towards the back
move back	stretch back a bowstring (on an archer's bow)
move away, as for privacy	use a surgical instrument to hold open (the edges of a wound or an organ)
	pull back or move away or backward