‘ And the border of the children of Dan went out from them. And the children of Dan went up and fought against Leshem, and took it and smote it with the edge of the sword, and possessed it, and dwelt in it. And they called Leshem, Dan, after the name of Dan their father.'
This note was not a part of the original surveyor's report, being added as a comment by the writer. ‘Went out from them' may signify that they were unable to expand to their borders, and were prevented from doing so. That is how LXX sees it (see below). The great constraint they were under comes out in their subsequent action. Many of them forsook the land God had given them and sought a better land, although some remained. This invasion of Laish (Leshem) is described more fully in Judges 17-18, and resulted in the setting up of the sanctuary of Dan. The whole disreputable story is recounted with obvious disapproval by the writer of Judges.
Laish was at the foot of Mount Hermon by the source of the Jordan to the north of the promised land, probably modern Tell el-Qadi (‘the judges' mound'). It had been settled since about 5000 BC and had been a wealthy city covering thirty acres, named in the Egyptian execration texts as rws, and in the Mari texts as Lasi. It was captured by Thutmose III. But it had allowed itself to become isolated and although it was reasonably strongly fortified with an earthen rampart, Dan ‘took it and smote it with the edge of the sword, and possessed it, and dwelt in it', renaming it Dan.
LXX places Joshua 19:48 immediately after verse 46 and then incorporates here material from Judges 1:34-35. It says ‘and the children of Dan did not drive out the Amorite who afflicted them in the mountain, and the Amorite would not allow them to come down into the valley, but they forcibly took from them the border of their portion. And the sons of Dan went and fought against Lachis, and took it, and smote it with the edge of the sword; and they dwelt in it, and called the name of it Lasendan. and the Amorite continued to dwell in Edom and in Salamin: and the hand of Ephraim prevailed against them, and they became tributaries to them.'
This whole incident brings home how difficult the Israelites were finding it when they sought to settle the valleys and plains where the Canaanites dwelt in comparatively large numbers. Joshua's victories had weakened Canaanite resistance but it had not destroyed it, and the delay in taking advantage of them had enabled Canaanite resistance to harden.