1)
What is the meaning of "Hashem Yiten Omer"?
1.
Rashi: Hashem says a message (the coming verses) aloud for the many legions of nations to hear.
2.
Malbim: Hashem made an announcement, and via this, great legions give good tidings to Yisrael.
2)
What are "ha'Mevasros Tzava Rav"?
1.
Radak (12-13): They are women who bear tidings. Women do not go to fight; they pray in the city and console the men with good words and consolation.