A paragraph break is appropriate here (so Revised Standard Version).

When Apollonius heard of it may be rendered “When Apollonius heard what had happened” (Good News Bible) or “When Apollonius heard what the Jewish army had done.”

He mustered three thousand cavalry and a large army: Mustered may be rendered “took” (Good News Bible) or “brought” (Contemporary English Version). For cavalry see the comments on 1Macc 1.17. Since cavalry is specifically mentioned, a large army obviously refers to foot soldiers, so Good News Bible says “a large army of infantry.”

And went to Azotus as though he were going farther: Azotus was a town on Mediterranean the coast about 12 kilometers (7.5 miles) south of Jamnia (see the comments on 1Macc 4.12-15). Apollonius heard that Jonathan was marching south to Jamnia, so he also headed south in a tactical move designed to lure Jonathan into more open country. Good News Bible overlooks as though he were going farther. A better model is “pretended to retreat, as if he were going to the south of Azotus.”

At the same time he advanced into the plain, for he had a large troop of cavalry and put confidence in it: Good News Bible has an excellent translation of this sentence, although it would be better to begin with “In fact, however….” Contemporary English Version‘s model is also helpful: “So he led his troops out to the nearby valley, where he was sure his cavalry could protect the soldiers.”

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.