Three years later, word came to Judas and his men that Demetrius, the son of Seleucus, had sailed into the harbor of Tripolis with a strong army and a fleet: Compare 1Macc 7.1. Three years later was 161 b.c. Word came to Judas and his men may be rendered “Judas and his soldiers heard [or, found out].” Demetrius is King Demetrius~I of Syria. He was the son of Seleucus~IV, and cousin of Antiochus~V (see the introductory comments on 1Macc 7.14). Tripolis was a city on the coast of Syria, well south of Antioch. For fleet see the comments on 1Macc 1.17.

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.