Richter 1:19

the Lord was with Judah; . . . but they could not drive out the inhabitants of the valley--The war was of the Lord, whose omnipotent aid would have ensured their success in every encounter, whether on the mountains or the plains, with foot soldiers or cavalry. It was distrust, the want of a simple and firm reliance on the promise of God, that made them afraid of the iron chariots (see on Jos 11:4-9).

And the Lord was with Judah,.... Encouraging, strengthening, succeeding, and giving the tribe victory over the Canaanites; the Targum is,"the Word of the Lord was for the help of the house of Judah:" and he drove out the inhabitants of the mountains; the mountainous part of Judea, such as was about Jerusalem, and where Hebron stood, and other cities, see Jos 15:48, &c. which though fortified both by nature and man, yet God being with them, they were easily subdued: but could not drive out the inhabitants of the valley; God forsaking them, because they were afraid of them, for a reason after mentioned, or through slothfulness, and being weary of fighting, or because they fell into some sins, which occasioned the divine displeasure; so the Targum,"after they had sinned, they could not drive out the inhabitants of the valley:" because they had chariots of iron; but this was no reason why they could not drive them out, if God was with them, who could as easily have delivered these into their hands, as the inhabitants of the mountains; but is the reason why they were afraid to fight with them, and to attempt to drive them out, and which they themselves gave why they did not.

I. Attitude of Israel Towards the Canaanites, and Towards Jehovah Its God - Judges 1-3:6 Hostilities between Israel and the Canaanites after Joshua's Death - Judges 1:1-2:5 After the death of Joshua the tribes of Israel resolved to continue the war with the Canaanites, that they might exterminate them altogether from the land that had been given them for an inheritance. In accordance with the divine command, Judah commenced the strife in association with Simeon, smote the king of Bezek, conquered Jerusalem, Hebron and Debir upon the mountains, Zephath in the south land, and three of the chief cities of the Philistines, and took possession of the mountains; but was unable to exterminate the inhabitants of the plain, just as the Benjaminites were unable to drive the Jebusites out of Jerusalem (vv. 1-21). The tribe of Joseph also conquered the city of Bethel (Jdg 1:22-26); but from the remaining towns of the land neither the Manassites, nor the Ephraimites, nor the tribes of Zebulun, Asher, and Naphtali expelled the Canaanites: all that they did was to make them tributary (Jdg 1:27-33). The Danites were actually forced back by the Amorites out of the plain into the mountains, because the latter maintained their hold of the towns of the plain, although the house of Joseph conquered them and made them tributary (Jdg 1:34-36). The angel of the Lord therefore appeared at Bochim, and declared to the Israelites, that because they had not obeyed the command of the Lord, to make no covenant with the Canaanites, the Lord would no more drive out these nations, but would cause them and their gods to become a snare to them (Jdg 2:1-5). From this divine revelation it is evident, on the one hand, that the failure to exterminate the Canaanites had its roots in the negligence of the tribe…

This chapter gives us a particular account what sort of progress the several tribes of Israel made in the reducing of Canaan after the death of Joshua. He did (as we say) break the neck of that great work, and put it into such a posture that they might easily have perfected it in due time, if they had not been wanting to themselves; what they did in order hereunto, and wherein they came short, we are told. I. The united tribes o Judah and Simeon did bravely. 1. God appointed Judah to begin (Jdg 1:1, Jdg 1:2). 2. Judah took Simeon to act in conjunction with him (Jdg 1:3). 3. They succeeded in their enterprises against Bezek (Jdg 1:4-7), Jerusalem (Jdg 1:8). Hebron and Debir (Jdg 1:9-15), Hormah, Gaza, and other places (Jdg 1:17-19). 4. Yet where there were chariots of iron their hearts failed them (Jdg 1:19). Mention is made of the Kenites settling among them (Jdg 1:16). II. The other tribes, in comparison with these, acted a cowardly part. 1. Benjamin failed (Jdg 1:21). 2. The house of Joseph did well against Beth-el (Jdg 1:22-26), but in other places did not improve their advantages, nor Manasseh (Jdg 1:27, Jdg 1:28), nor Ephraim (Jdg 1:29). 3. Zebulun spared the Canaanites (Jdg 1:30). 4. Asher truckled worse than any of them to the Canaanites (Jdg 1:31, Jdg 1:32). 5. Naphtali was kept out of the full possession of several of his cities (Jdg 1:33). 6. Dan was straitened by the Amorites (Jdg 1:34). No account is given of Issachar, nor of the two tribes and a half on the other side Jordan.