And they came and besieged him in Abel of Bethmaachah
That is, Joab and Abishai, with the forces under them, who pursued him hither:
and they cast up a bank against the city;
which some understand of a warlike machine or engine, with which stones were cast; but it rather seems to be a bank of earth thrown up, for the better working of such engines to more advantage against the city, by throwing from thence darts into the city, or stones against the walls of it, to batter it down; such banks were used in sieges, as that Caesar's soldiers raised in twenty five days, which was three hundred thirty feet broad, and eighty feet high F26; Kimchi interprets this of filling up the ditches round about the city with dust and earth, and so making it level, whereby they could come the more easily to the walls and batter them, or scale them, and take the city by storm:
and it stood in the trench;
the army under Joab stood where the trench round the city had been, now filled up:
and all the people that [were] with Joab battered the wall to throw it
with their engines, or whatever battering instruments they had; so, often, as Hesiod F1 says, a whole city suffers for one bad man.
F26 Caesar. Comment. l. 7. c. 24.
F1 Opera & Dies, l. 1. ver. 236.