"...with God all things are possible."
KJV: And the LORD was with Judah; and he drave out the inhabitants of the mountain; but could not drive out the inhabitants of the valley, because they had chariots of iron.
NIV: The LORD was with the men of Judah. They took possession of the hill country, but they were unable to drive the people from the plains, because they had iron chariots.
Many responses to Judges 1:19 point out that the pronoun "he" in the KJV refers to Judah, not God (as is illustrated in the NIV). However, I think there is something more to this alleged contradiction, namely, "If God was with Judah (e.g. giving them favor) and God is omnipotent, why couldn't Judah stand up against people with iron chariots?"
A possible explanation for this comes from Joshua 17:14-18:
The people of Joseph said to Joshua, "Why have you given us only one allotment and one portion for an inheritance? We are a numerous people and the LORD has blessed us abundantly."
"If you are so numerous," Joshua answered, "and if the hill country of Ephraim is too small for you, go up into the forest and clear land for yourselves there in the land of the Perizzites and Rephaites."
The people of Joseph replied, "The hill country is not enough for us, and all the Canaanites who live in the plain have iron chariots, both those in Beth Shan and its settlements and those in the Valley of Jezreel."
But Joshua said to the house of Joseph - to Ephraim and Manasseh - "You are numerous and very powerful. You will have not only one allotment but the forested hill country as well. Clear it, and its farthest limits will be yours; though the Canaanites have iron chariots and though they are strong, you can drive them out."
It appears the plain country was not part of the original inheritance given to Israel, thus it may not have been God's intention to give it to the tribe of Joseph.
Other responses (offsite)