“Judas was encamped in Elasa. With him were three thousand picked men. When they saw the huge number of the enemy forces, they were greatly frightened. Many slipped away from the camp, until no more than eight hundred of them were left.”
Now we see the problem. Judas Maccabeus was at Elasa, which was close to Beth-horon. However, he only had 3,000 men. However, when they saw the 22,000 men coming at them, another 2.200 men deserted Judas until he was left with only 800 men. This does not look good.