Q: When troops are deployed, does that mean that they were previously ployed?
A: In technical military writing, the verbs “deploy” and “ploy” have sometimes been used in contrasting ways.
“Deploy” has meant “to spread out (troops) so as to form a more extended line of small depth” while “ploy” has meant “to move (troops) from line into column,” according to the Oxford English Dictionary.
However, only two of the ten standard dictionaries we regularly consult, Collins and Dictionary.com, have entries for the verb “ploy,” and both describe it as an archaic military term.
(The OED is an etymological dictionary based on historical evidence; standard dictionaries focus on language as it’s used now.)
The US Defense Department’s Dictionary of Military and Associated Terms (November 2021), doesn’t have entries for “ploy” or “ployment,” and it defines “deployment” as the “movement of forces into and out of an operational area.
Here’s the earliest OED citation for the old military sense of the verb ploy:
“In the march by echellons, the battalions may be ployed into columns with deploying intervals, as in a full line” (Army and Navy Chronicle, March 17, 1836).
And this is the first Oxford citation for “deploy” used in its old military sense:
“His columns … are with ease and order soon deploy’d” (“Progress of War,” a poem in The European Magazine, 1786, by an officer identified as “Lieutenant Christian”).
The two old military terms were undoubtedly influenced by the earlier French use of ployer and déployer in the same sense in a treatise on military tactics, Essai Général de Tactique (1772), by Jacques-Antoine-Hippolyte, Comte de Guibert.
When “deploy” entered English in the 15th century, it briefly meant the same thing as the earlier word “display”—to unfold or spread out. In fact, “deploy” was merely a different way of spelling “display.”
So if either “deploy” or “display” had an etymological opposite based on the same Latin roots, it would be “ply” (to fold or layer).
Both words come ultimately from the Latin displicare, which is composed of the negative prefix dis– (un-) and plicare (fold).
This is also the ancestor of “ply,” “apply,” “comply,” “complicated,” “employ,” “imply,” “pleat,” and “splay,” according to the OED and John Ayto’s Dictionary of Word Origins.
So why did we once, very briefly, have these two words for the same thing? You might call it a printer’s idiosyncrasy.
The Latin verb displicare made its way into Old French (as desplier, later desployer), and from Old French it passed into Middle English in the 1300s as desplay (later spelled “display”).
In the late 1400s, the printer William Caxton chose to spell this word in the Parisian fashion: “deploye” and “dysploye.”
But Caxton’s variations, credited with being the first uses of “deploy,” didn’t really establish the word in English. As the OED explains, the actual adoption of “deploy” in a specific sense didn’t take place until the end of the 18th century.
That’s when “deploy” acquired its original military meaning (“to spread out (troops) so as to form a more extended line of small depth”).
So we might think of a line of “deployed” troops at that time as being unfolded or spread out.
[Note: This post was updated on Feb. 5, 2023.]