“ready and armed for war crossed over.” The people from Reuben, Gad, and half the tribe of Manasseh made good on their promise and crossed over Jordan to help the rest of Israel claim their inheritance (Josh. 1:12-18).
“in the presence of Yahweh.” The ark, representing God, was in the Jordan River when the people crossed over.
“to the plains of Jericho.” The “plains of Jericho” is the flat land in the Arabah, the Jordan valley, just north of Jericho. The Hebrew word for “plains” comes from the word “mixed.” The area might well have been known as “mixed” because there are patches of gray, brown, and green, in part due to the agriculture and vegetation there from springs, streams, and the Jordan itself.