The Israelites, under Joshua’s guide did not conquer every piece of territory in which the 7 Canaan tribes – by God execrated - resided. Joshua himself – by that time – very old, encouraged his men to continue battling for God (see, please his talk in the 13th chapter of his book). Afterward, Joshua, did admit in all honesty, that pockets of resistance remained (Jos 16:10; 17:11-13). In one occasion – at least – Joshua appeared bothered with the lack of initiative and divine courage showed by the descendents of Joseph. Responding to their complain about the smallness of the territory assigned to them, he said to them: “If [אם] you are such a great people [like you claim], go up into the woodlands, clearing a place there for yourselves in the land of the Perizzites and the Rephaim, if the hill-country of Ephraim is not wide enough for you.” [Bible in Basic English]”.
And also after the Joshua’s death (Kri [Judges] 1:17-21; 3:1-6) the Conquest wasn’t completed. In fact, Kri 1:28-33 reported - 5 times - the negative sequence הורישׁ לא, ‘[This or that tribe] drove not out [this or that Canaanite people]’. Moreover, in the same verse 28, the reading is more forthright than ever,
והורישׁ לא הורישׁו
‘but, regarding the driving out of them [Canaanites], they [the Israelites] did not drive them out [completely]’.
Nevertheless, though many of the Canaanites survived the major conquest and resisted subjugation, it could still be said that: “[…] the LORD [יהוה] gave unto Israel all the land which He swore to give unto their fathers; and they possessed it, and dwelt therein. And the LORD [יהוה] gave them rest round about, according to all that He swore unto their fathers; and there stood not a man of all their enemies against them; the LORD [יהוה] delivered all their enemies into their hand. There failed not aught of any good thing which the LORD [יהוה] had spoken unto the house of Israel; all came to pass.” (Jos 21:43-45, JPS).
This happened why, all around, the Israelites broke the tight unity the enemy peoples did possess, so they offered yet no hard threat to the Israelites’ security. Any failure of the Israelites finally to take certain territories could not be charged to IEUE’s account as a failure on his part to fulfill his promise. (Jos 17:16-18; Kri 4:13). We have to remember – always - that the record shows that the Israelites’ defeats were due to unfaithfulness on their part (Num 14:44-45; Jos 7:1-12), because God had warn them - in advance - that their (future) victories (so, really, the IEUE’s participation to the battles) would depend on their obedience to His laws and guidelines. So, the Conquest was a conditional goal to be attained.
I am not agree with you (Niclas Nilsson), when you say, ‘It's pretty likely that Joshua 10 is hyperbole. Ancient writings often exaggerated the accomplishments of kings in this way.’ Granted, various ancient kings exaggerated their victories stories. For an example, Yuval Noah Harari remember us that “Sargon [of Assyria] boasted that he had conquered the entire world. In reality, his dominion stretched from the Persian Gulf to the Mediterranean. […] For the next 1,700 years Assyrian, Babylonian and Hittites kings adopted Sargon as a role model, boasting that they, too, had conquered the entire world.” [Sapiens: A Brief History of Humankind].
I don’t see, however, any similar boasting in the Joshua historical recording. Would he did mention the abovementioned Israelites’ conquest failures if he did want ‘hyperbolize’ the global war report?
Finally, the idea - Lawrence E. Stager-expressed - that the Conquest did not really happen, is (for my viewpoint) one of the various attempt to ridiculize the Bible account as non-historical text. I encourage smart users – before to reach any conclusion about this important topic – to read (as just a taste of huge literature on behalf of Bible historical reliability) the fine books by historian and archaeologist David Rohl, especially, A Test of Time – The Bible From Myth to History (chapter 14, in particular), along with The Lost Testament (chapter 11, in particular).
P.S. I apologize for my wobbly English.