John Calvin Commentary Joshua 10:1

"Now it came to pass, when Adoni-zedek king of Jerusalem heard how Joshua had taken Ai, and had utterly destroyed it; as he had done to Jericho and her king, so he had done to Ai and her king; and how the inhabitants of Gibeon had made peace with Israel, and were among them;" — Joshua 10:1 (ASV)

Now it came to pass, etc. He had previously briefly touched upon, but now more fully details the conspiracy of the kings who lived both in the mountains and in the plain. For after mentioning that they were struck with fear and allied together to wage a common war, he had stopped suddenly and proceeded to speak of the Gibeonites.

What he had previously said of the kings in general, he now applies only to one individual. This was not because Adoni-zedek alone was afraid, but because he stirred up all the others and was the main instigator and leader in carrying on the war against the Israelites. This is sufficiently expressed by the plural form of the verb, for it is said, When Adoni-zedek had heard—they feared greatly. From this, it appears that they were all of the same mind. However, while some of them held back from fear, the one who possessed greater authority and was closer to the danger invited the four others to arms.

In the beginning of the chapter, it is again told how the five kings formed an alliance to confront the Israelites and avert the overthrow with which they were all threatened. But as the Gibeonites had meanwhile surrendered, the kings first turned their arms against them, aiming both to inflict punishment upon them as traitors to their country (thus making them an example to all their neighbors), and also to inspire their own soldiers with confidence by striking terror into those vanquished enemies. Therefore, they resolved to attack the Gibeonites who, by their embassy, had caused a disruption and opened a way for the Israelites.

Indeed, they had a plausible pretext for war in their resolve to punish the cowardice of those who had chosen to side with strangers (who were about to lay the whole country waste) rather than faithfully defend their neighbors. And the Gibeonites experienced how useless their clever plan would have been if they had not been saved in pity by the Israelites. Meanwhile, the Lord allowed them to be involved in danger so that, being freed twice, they might more willingly and meekly submit to the yoke.