Albert Barnes Commentary 2 Kings 25:4

"Then a breach was made in the city, and all the men of war [fled] by night by the way of the gate between the two walls, which was by the king`s garden (now the Chaldeans were against the city round about); and [the king] went by the way of the Arabah." — 2 Kings 25:4 (ASV)

The city was broken up - Rather, “broken into,” that is, a breach was made around midnight in the northern wall (Ezekiel 9:2), and an entry was made into the second or lower city (see the note on 2 Kings 22:14), which was protected by the wall of Manasseh (2 Chronicles 33:14).

A precipitate flight followed the advance of the Babylonians to the “middle gate,” the gate of communication between the upper and lower cities. This position was just north of the royal palace, which the king therefore left. He escaped by the royal garden at the junction of the Hinnom and Kidron valleys, passing between the two walls that flanked the Tyropoeon valley.

Toward the plain - This refers to “the Arabah,” the great depression that borders Palestine on the east (see the note on Numbers 21:4). The “way toward the Arabah” is the road leading eastward over the Mount of Olives to Bethany and Jericho.