Revised Standard Version begins a new paragraph here, but there doesn’t seem to be any good reason for doing this.

Then Jonathan with his men, and Simon, withdrew to Bethbasi in the wilderness: Jonathan suspected Bacchides would be eager to punish him for killing 50 of his sympathizers, so he went into the open country south of Jerusalem to escape and prepare a defense. Simon has not been mentioned since verse 37, so it may be helpful to say “Simon his brother.” Bethbasi was a village with an abandoned fort just to the southeast of Bethlehem, not far from Tekoa (see verse 33). It was possibly one of the forts built by King Uzziah (2~Chr 26.10). For wilderness see the comments on 1Macc 2.29. An alternative model for this clause is “Then Jonathan, Simon [his brother], and their men escaped to Bethbasi in the wilderness.”

He rebuilt the parts of it that had been demolished, and they fortified it: A suggested model is “They rebuilt the parts of the old fort that had been destroyed, and strengthened its defenses.” Another possible model is “Part of the old fort had been destroyed, but they repaired it and strengthened the walls and the gates.”

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.