He went to meet them may be rendered “So Jonathan set out to attack the army of Demetrius” (similarly Contemporary English Version).

But left his brother Simon in the country: We assume that the country refers to Judea, so this clause may be translated “while his brother Simon stayed behind in Judea.”

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.