'Armies' in the Bible

"You know what Joab son of Zeruiah did to me -- how he murdered two commanders of the Israelite armies, Abner son of Ner and Amasa son of Jether. During peacetime he struck them down like he would in battle; when he shed their blood as if in battle, he stained his own belt and the sandals on his feet.

The armies were deployed opposite each other for seven days. On the seventh day the battle began, and the Israelites killed 100,000 Syrian foot soldiers in one day.