Here are some of my thoughts from sermon notes on the passage:
Judges ch.1 has a "two tone" effect. Early in the chapter, Judah’s progress is marked as they moved through the various geographic or topographic areas covering of their allotted territory, settling it while mopping up persistent remnants of the Canaanites. The last word in v17 showed them fulfilling a curse of the LORD against the evil inhabitants of Zephath (on their) SE flank. This threatening promise God declared as Israel was making its way on the final legs of her wilderness wandering.
All that remained for Judah’s complete scouring of the Canaanites was the Philistine presence along the coast. V18 records their apparent success in this venture. From the south to the north, they rolled them up and drove them away before them. Three cities are mentioned: Gaza (at the southern end), Ashkelon in the center, and Ekron at the northern end (so we infer; today its exact location remains an enigma). Ekron is also named among the cities of Dan’s inheritance just north of Judah, so it stands to reason it was near the border. But there were five cities of the rulers of the Philistines (Jos.13:3), including Gath and Ashdod. What of them?
We might infer that they were just part of that campaign; however, we have the statement of v19 that—whatever the successes were in taking those three cities and territories—still Judah could not drive out all the inhabitants of the lowland, because of the chariots. This is in spite of what Scripture says, Ps. 68:17, “The chariots of God are twice ten thousand, thousands upon thousands; the Lord is among them; Sinai is now in the sanctuary.” What then is iron before the melting fire of Sinai?
V20 speaks again of the expulsion of Anak from Hebron, the power of God shown in Caleb’s faith prevailing there. But those who knew Israel’s longer history knew that Gath was the city of Goliath, a remnant of the Anakim who terrorized Israel until the boy David struck him down. Also, by the time we get to Jdg.16, in the midst of the story of Samson, the Philistines are in Gaza, and quite comfortable it seems. So, what v18 reveals is a victory that only seems to be complete, but hides a fatal flaw. V19 starts to strip the secret bare.
כִּ֣י לֹ֤א לְהוֹרִישׁ֙ אֶת־יֹשְׁבֵ֣י הָעֵ֔מֶק כִּי־רֶ֥כֶב בַּרְזֶ֖ל לָהֶֽם׃
Yet not (they) to drive out inhabitants of lowland because chariots of iron to them.
Still, they did not drive out the prior-dwellers of the lowland region because they had chariots of iron.
Attend now to the first part of v19,
וַיְהִ֤י יְהוָה֙ אֶת־יְהוּדָ֔ה וַיֹּ֖רֶשׁ אֶת־הָהָ֑ר
So it happened the LORD (was) with Judah--and they took possession of the hill-country...
I draw from this disjuncture not that the LORD was only with Judah part of the time, but that Judah only trusted the LORD so far. They may have been better than all the other tribes, but still they trusted in themselves; and as they did so, they lost confidence and experienced only limited success.
V21 then repeats the fact of the persistence of the Jebusites in Jerusalem (as previously stated in Jos.15:63), but makes it especially Benjamin’s failure, after Judah’s success there in v8. This starts a litany of the failures of almost all the other landed western tribes. Only Issachar is missing from this list of tribes and their failures. It isn’t a complete list of nothing but failure. In particular, Ephraim’s triumph at Bethel is recorded,as a kind of parallel to Judah’s strong showing. “The LORD was with them,” v22. Spies captured a man of the place who exposed the city’s vulnerabilities (the “entrance”), in exchange for his life and his family.
So, Ephraim is credited, but his brother tribe Manasseh (previously noted in Jos.17 as lacking faith and fortitude) is noted for how many Canaanite cities were left to them. Their “determination” is noted against him, v27. Putting them to tribute and second-class status is mentioned (after Israel was “strong”), but this was only half-obedience, and not even that. Furthermore, the example is also found in Ephraim, v29. So, the commendation becomes condemnation.
Zebulon is next, “Nor did Zebulon…” v30. “Nor did Asher,”vv31-32. But here it is said, not that the Canaanite dwelt among the Israelites, but the Israelites dwelt among the Canannites. The same is said of the next tribe, “Nor did Naphtali,” v33, and “they dwelt among the Canaanites.” It mattered not that Israel was stronger, and put the Canaanites to labor. The inspired verdict is that the land was effectively not theirs at all, but remained Canaanitish.
Finally, Dan’s record is mentioned, how they proved completely unable to handle the Amorites. They forced the Danites into the mountains, and they dwelt securely in places from which Joshua had had some of his most remarkable success, the fight after the defense of Gibeon, when the sun stood still over the valley of Aijalon. What a sad witness, as God’s people turned their back on the great success of Joshua.
The Amorites were determined to have their way, v35, and not the people of God, with the promise of God at their back, and going before them. When, over time, the Amorites were overwhelmed by Israelite numbers, they paid a price, but did not leave. They were like an evil leaven amid the holy people.
The conquest was not imperfect on account of divine failure. Rather, we have to place the fault where it surely lies, with the people and their foolhardy boasts that they could keep up their promises under the covenant in their own strength, by their own determination. Heb.8:8 states the fact clearly when it says he (God) found fault with them. The author is reflecting on a very late moment in the life of the covenant nation, as Jeremiah records the catastrophic end of the theocracy; and the LORD speaks of the need for a “new covenant.”
The old covenant’s (Sinai’s) presentation, its outward form, was legal and demanding (though we should say, its substance or inner hidden nature was grace). It was well-suited for that purpose under which it was given, but it had a terminus, an end-date. It was preparatory for the coming of the Christ. In that sense, it was defective, as it was not permanent and everlasting. In itself, it was flawless; however, it did not have any power to transform the heart, to make or persuade its subjects to love God. So, if the humans entering the covenant, offering to do their part to maintain it, were themselves unrighteous: they could not hope to have success.
We have here the evidence (thus far) of Judges "two-tone" reality for life-in-the-land (typological land) of rest. What success the people have is by divine strength, by faith and trust, a carrying forward of the overall tone of the book of Joshua. What failure the people have is when they seek their own, and success on their own. They cannot accomplish by might what can only be got by grace (which is a lesson their father Jacob/Israel was taught many generations prior).
