Now Jeroboam had sent troops around to the rear, so that while he was in front of Judah the ambush was behind them. (NIV)
But Jeroboam caused an ambushment to come around them from behind, so his troops were before Judah and the ambush behind. (AMP)
But Jeroboam caused an ambushment to come about behind them: so they were before Judah, and the ambushment was behind them. (KJV)