When his men who were fleeing saw this: The demonstrative pronoun this refers to the fleeing enemy soldiers. We may render this clause as “When the Jewish soldiers who had deserted saw the enemy fleeing [or, trying to escape].”

They returned to him and joined him in the pursuit may be expressed as “they returned and helped Jonathan and the other soldiers chase the enemy.”

As far as Kadesh, to their camp, and there they encamped: Their camp refers to the enemy camp at Kedesh. When Jonathan’s men reached that point, they stopped the pursuit, knowing that the enemy was on the run. Good News Bible renders and there they encamped as “and then took over the camp.” A better model for this clause is “and they set up their own camp there.”

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on 1-2 Maccabees. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here.