‘ Joshua therefore came on them suddenly, for he went up from Gilgal all night. And YHWH discomfited them before Israel and slew them with a great slaughter at Gibeon, and chased them by the way of the ascent of Bethhoron, and smote them to Azekah, and to Makkedah, and so it was that as they fled from before Israel, while they were on the descent from Bethhoron, YHWH cast down great stones from heaven on them, to Azekah, and they died. They were more who died with the hailstones than they whom the children of Israel slew with the sword.'
Joshua made a sudden surprise attack, having travelled by forced marches through the night for the purpose, and would have caught the enemy napping, something which resulted in great slaughter and a precipitate flight They chased them up the ascent of Bethoron, while some of the Canaanite forces fought a rearguard action to allow their comrades to escape. But there was no escape from YHWH, for as their comrades sought to escape down the descent on the other side of Bethhoron, great hailstones fell from heaven and decimated the fleeing forces, so much so that more died by this means than in the actual fighting.
Note the combining of the activity of YHWH with the people of Israel. In one sense it was all the work of YHWH, in another much of it was the activity of Israel. Great hailstones the size to kill a man, especially when they were descending hazardous paths, fell on the retreating troops. Such huge hailstorms have been known in the Mediterranean region where hailstones weighing more than twelve pounds each have been known to fall (compare Revelation 16:21). Defeat in this way was devastating for the Amorites. One of their main gods was Baal, Lord of rain and of storm. Yet here he seemed unable to help them against the might of YHWH.
The site of Azekah is unknown but its signal lights could be seen from Lachish in the days of Sennacherib of Assyria.