Q. The Naval War College Writing and Style Guide states: “Although a term may be plural or possessive, do not make the abbreviation plural or possessive on first usage: cluster bomb units (CBU).” Is that also The Chicago Manual of Style’s preferred convention for first appearance of an acronym in a document?

A. Although CMOS is silent on this topic, the plural “cluster bomb units (CBUs)” looks respectable. The possessive, however, would be awkward: “cluster bomb unit’s (CBU’s).” Reword to avoid it.