Judges 1:1-2:5

The LORD tells them that Judah has been chosen to take care of the Canaanites,
and the tribe of Judah asks the tribe of Simeon to help them and in return Simeon
will receive aid from Judah when they take their inheritance. There are successes
and there are failures in this passage.

First, let's look at the successes and why they were successful:

Judah was successful 1:19: "The LORD was with the men of Judah"
Joseph was successful: 1:22 "...and the LORD was with them"

Out of the tribes that this passage mentions, only these two (three, if you count Simeon as assumed because of the Judah/Simeon alliance) tribes are singled out to say that the LORD was with them. A big key to success: The LORD must be with you.

Okay, that seems like a no-brainer, but how is it that the LORD was with some and not with others when the entire nation was going about the work of conquering the promised land? Did not God promise them the land? Are they not in His will when they are going forth to conquer? Well, let us look at the reasons given for failure

Reasons given for the failures:
(In the order they are mentioned)

1. The Canaanites posses superior weapons.
1:19b "but they were unable to drive the people from the plains, because
they had iron chariots."

2. The Canaanites were determined to live in the land.
1:27 "for the Canaanites were determined to live in that land"
1:35 "And the Amorites were determined also to hold out in Mount Heres"

3.Israelites disobeyed God
2:2 "'and you shall not make a covenant with the people of this land, but you shall break down their alters.' Yet you have disobeyed me."

I believe number three to be the over-arching reason Israel failed to drive
the Canaanites completely from the promised land. God can overcome the first
two, and there are places in the Bible where it is recorded that He did. But
because the Israelites disobeyed, God was not with them to give them the victory.
When you go without God and you are left to fight a battle in your own strength,
it is hard to defeat an enemy who possesses better weapons and is determined
to win.