Who were the 40,000 men armed for battle?

In the Old Testament, 40,000 is a round number meaning a large army (Judges 5:8; 2 Samuel 10:19; 1 Chronicles 19:18; 1 Kings 4:26; 1 Chronicles 12:36).¹

It is unclear if the text refers to only the three tribes as being 40,000 or if that is the total number of armed men from all the tribes of Israel. Most likely, it is the total number. Even then, there is some debate about whether or not our translation of the Hebrew word for thousand (eleph) is correct. Perhaps this word should instead be understood as referring (at times) to a military grouping rather than a literal number. Along with the Hebrew word for hundred (me’ah), these two terms are used elsewhere in the Bible in a way that is similar to terms for military units like legion, squadron, battalion, or platoon (Numbers 31:5; 1 Samuel 8:12; 1 Samuel 29:2; 2 Samuel 18:1; 2 Kings 11:4). If this is the case, then we do not know exactly how many men crossed over armed for battle.