field of battle vs battleground

field of battle and battleground both are nouns.

Word	Noun	Adjective	Verb	Adverb
field of battle	Yes	No	No	No
battleground	Yes	No	No	No

As nouns, field of battle and battleground are synonyms defined as:

field of battle and battleground: a region where a battle is being (or has been) fought

Other synonyms of field of battle include battlefield, field, field of honor.

field of battle (noun)	battleground (noun)
a region where a battle is being (or has been) fought	a region where a battle is being (or has been) fought