Judges 1:19

With Judah. Judah was able to succeed only partially because of a seeming superiority in the weapons of the enemy. Why was this when chariots of iron are nothing before the might of God, whose chariots are ten thousands of angels? Infinite power was available, yet the tribe of Judah was not able to gain complete mastery over its enemies. The author of the book of Judges later explains why (see on ch. 2:14-23).

Chariots of iron. On the mountains where horses and chariots could not maneuver, the mobile, daring bands of Hebrews were victorious; but in the broad valleys of the maritime plain the better armed Canaanites were able to repel their incursions. The use of iron was just becoming common among the Canaanites, who were ahead of the nomadic Hebrews in the art of metal working. They had recently learned the use of chariots and horses from the Hittites and Hurrians, and employed them to good advantage against the foot soldiers of the Hebrews, who were unable to cope with this superior weapon.