Sentence:  Although it was at the Battle of The Little Horn , about which more words have been written than any other battle in American history , that the 7 th Cavalry first made its mark in history , the regiment <WSD>was</WSD> ten years old by then . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)