the city was broken up - that is, a breach was effected, as we are elsewhere informed, in a part of the wall belonging to the lower city (2Ch 32:5; 2Ch 33:14).
the men of war fled by night by the way of the gate between two walls, which is by the king’s garden - The king’s garden was (Neh 3:15) at the pool of Siloam, that is, at the mouth of the Tyropaeon. A trace of the outermost of these walls appears to be still extant in the rude pathway which crosses the mouth of the Tyropaeon, on a mound hard by the old mulberry tree, which marks the traditional spot of Isaiah’s martyrdom [Robinson]. It is probable that the besiegers had overlooked this pass.
the king went ... toward the plain - that is, the Ghor, or valley of Jordan, estimated at five hours’ distance from Jerusalem. The plain near Jericho is about eleven or twelve miles broad.