In Joshua 14:6 - 15, we read that, after 7 years of conquest, Joshua gave Hebron to Caleb as an inheritance. Up until verse 12, chapter 15 describes the rest of Judah's allotment. Verses 13 - 19 turns back to the topic of Caleb's inheritance by informing us of Caleb's capture of Hebron and his nephew Othniel's capture of Debir.
Judges 1 is where things go wrong. Here's a basic summary on what transpires in these verses:
Joshua dies and Judah takes the lead in the war against Canaan. They start off by capturing the city of Bezek and her king, who they will mutilate and take to their next target, Jerusalem, where he will die. Once Jerusalem's burnt, we read that Judah turns her attention to "the hill country, the Negev and the Judean foothills." They then proceed to attack Hebron and defeat Anak's three sons. Then we get to Debir, where Caleb again offers his daughter in exchange for its capture and where his nephew Othniel again accepts it.
There's the issue. Joshua 14-15 places Caleb & his nephew's conquests during Joshua's lifetime while Judges 1 places it after his death. There are three solutions I've come across for this issue:
These are two different conquests of Hebron & Debir. I read this a while ago so I may be misremembering but if I'm not, then this is a ridiculous attempt. The two accounts are identical.
Judges is pointing back to something that happened during Joshua's lifetime. I'm not exactly sure how this would be possible. The narrative makes no indication that it's telling anything other than a straightforward account of the events immediately following Joshua's death.
Joshua is pointing forward to something that will take place after Joshua's death. I think this explanation is most likely correct as, in my opinion, there's a good deal of wiggle room in this portion of Joshua. There is, however, a problem with this approach: Caleb's request clearly comes during Joshua's lifetime and apparently while the land is being divided. This third option requires us to believe that Caleb, who was 85 at the time of his request, waited years or decades to claim his land.