buckle under vs succumb

buckle under and succumb both are verbs.

Word	Noun	Adjective	Verb	Adverb
buckle under	No	No	Yes	No
succumb	No	No	Yes	No

As verbs, buckle under and succumb are synonyms defined as:

Other synonyms of buckle under include give in, knuckle under, yield.

buckle under (verb)	succumb (verb)
consent reluctantly	consent reluctantly
	be fatally overwhelmed