The Lord gave the word. The reader naturally asks—What word? Commentators answer variously: "the watchword" (Cheyne); "promise of victory" (Kay); "the word of command" (Dean Johnson); "announcement of an actual victory gained" (Hengstenberg).
I should rather understand a sort of creative word, initiating the period of strife (comp. Shakespeare's "Cry havock, and let slip the dogs of war!"). Great was the company of those that published it; literally, great was the company of the women that heralded it.
The reference is to the female choirs which took a prominent part in the war songs of ancient days (see Exodus 15:20, Exodus 15:21; 5:1; 1 Samuel 18:6, 1 Samuel 18:7).