When Demetrius the king heard of it: Heard of it may be expanded to “heard [or, found out] that Alexander was in the city of Ptolemais.”
He assembled a very large army and marched out to meet him in battle: The author has left us with a narrative problem here, which the translator may not be able to solve. With this verse, the reader is prepared to hear about a battle between Demetrius~I and Alexander. However, the battle does not occur until verse 49. In verse 48 we read that Alexander gathered his forces, as Demetrius does here. Everything we read in verses 3-47 apparently took place while Demetrius was on his way south from Antioch, which was about 385 kilometers (240 miles) north of Ptolemais. There is probably nothing the translator can do to help the reader understand that the battle is not going to take place immediately, but a paragraph break at the end of this verse would at least be helpful, and we highly recommend it. He assembled a very large army may be expressed as “he gathered together a huge number of soldiers.” And marched out to meet him in battle may be rendered “and led them out to attack him [Alexander].”
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.