The sons of Reuben and Gad had many animals and they looked upon the land of Jazer and Gilead as good pasture for their animals and so they came to Moses and Eleazar and the princes of the community.

The land Ataroth, Dibon, Jaser, Nimrah
Heshbon, Elealeh, Sebam, Nebo and Beon
Who the Lord vanquished before the community of Israel is good pasture and we have many animals. Give us this land and let us not move across the Jordan. However, Moses spoke to them, your brothers will go to war and you want to stay here? Why do you discourage the hearts of the Israelites from moving into the country that the Lord has given them.
You fathers also did thus when I sent them to Kadesh Barnea to survey the land. After they has come down to the Eshkol stream they discouraged the hearts of the Israelites. The wrath of the Lord rose because they did not wish to enter the land that the Lord had selected for them. And the Lord swore that he would not let them see the land because they had not followed him loyally. The only exceptions were Caleb and Joshua So the wrath of the Lord burned against Israel and he caused them to wander back and forth across the desert for forty years until all that had done evil before the Lord were gone. And behold, you stand in place of your fathers that the sins become more our own and you also bring more of the wrath of the Lord upon yourselves. For when you turn away from him he will cause your people to remain even longer in the desert, and you will pass away entirely.
Then they approached: we would only like to build pens for animals and cities for our children. However, we will go armed before Israel until we have brought them to their place. However, our children shall stay in fortified cities because of the inhabitants of the land. We do not want to return home until each has received his inheritance, for we do not want to share their inheritance beyond the Jordan but to the east on this side.

Moses said: if you wish to do this then arm yourselves for battle before the Lord. He who is armed will cross the Jordan and drive out his enemies that the land is subdued before the Lord.
After that you may return without sin before the Lord. Do this not, you sin against the Lord. Your sins will find you. So do what you have said.
The Sons of Gad and Reuben said to Moses: your servants will do as my Lord has commanded. All of our children, women, our possessions and animals shall remain in the city of Gilead. While we go to battle as an armed army.
Then Moses commanded the priests Eleazar and Joshua and leaders of each tribe and said: when the sons of Gad and Reuben have crossed over the Jordan with you and gone armed into battle before the Lord and the land has been subdued, give them the land of Gilead as their own. If they do it not, go armed alongside you, they shall share your inheritance in the land of Canaan. Gad and Reuben answered: as the Lord commands his servants, we shall do.
So Moses gave the sons of Gad and Reuben and the half tribe of Manasseh the kingdom of Sihon, king of the Amorites and the Kingdom of Og King of Basan, the land and the cities around it and the entire area. Gad built: Dibon, Ataroth, Aroer, Atroth Shophan, Jazer, Jogbehah, Beth Nimrah, Beth Haran fortified cities and pens.

And the sons of Reuben built Heshbon, Elealeh and Kiriathaim, Nebo and Baal Meon and Sibmah and gave the cities the names they had had. The Sons of Makir, (son of Mannaseh) went to Gilead, conquered it, and drove out the Amorites. Then Moses gave Makir Gilead, wherein he resided. However, Jair, son of Manasseh went there and conquered its villages. He named them “the villages of Jair”.
Nobah went there and conquered Kenath and its settlements and named it Nobah after himself.