2 Chronicles 13:3
And Abijah set the battle in array with an army of valiant men of war, even four hundred thousand chosen men: Jeroboam also set the battle in array against him with eight hundred thousand chosen men, being mighty men of valour.
Cross-reference
2 Chronicles 13:17
Parallel
In 2 Chronicles 13:17, the battle's outcome is described — Abijah's army slaughters 500,000 Israelites, fulfilling the conflict set up in verse 3.
2 Chronicles 11:1
Historical context
2 Chron 11:1 describes Rehoboam assembling a large army against Jeroboam, the same conflict Abijah now faces.