“ And I brought you into the land of the Amorites, who dwelt Beyond Jordan, and they fought with you, and I gave them into your hand, and you possessed their land, and I destroyed them from before you.”
Now they were reminded of more recent events which all of them could remember, how God had enabled them to defeat the Amorites, who would not let them pass peacefully but had fought with them. And He had enabled them to possess their land (Numbers 21:21-24).