ANTIETAM WAS THE MOST DEBASTATING ONE -DAY BATTLE OF THE CIVIL WAR.

IN THAT SENTENCE WAS IS THE VERB BUT IS IT CONNECTION ANTIETAM AND BATTLE-LINKING VERB

2 answers

Please use lower-case letters. When you use capital letters, it is harder to read and in computer language, considered impolite, like shouting.

Sra
Note the spelling of "devastating" ("v" not "b").

Yes, the verb is "was" and it is the linking verb connecting "Antietam" and "battle."