This chapter opens with these words, what struck me was the northern extent of the land to the great river Euphrates.
Deuteronomy 1King James Version (KJV)
1 These be the words which Moses spake unto all Israel on this side Jordan in the wilderness, in the plain over against the Red sea, between Paran, and Tophel, and Laban, and Hazeroth, and Dizahab.
2 (There are eleven days’ journey from Horeb by the way of mount Seir unto Kadeshbarnea.)
3 And it came to pass in the fortieth year, in the eleventh month, on the first day of the month, that Moses spake unto the children of Israel, according unto all that the Lord had given him in commandment unto them;
4 After he had slain Sihon the king of the Amorites, which dwelt in Heshbon, and Og the king of Bashan, which dwelt at Astaroth in Edrei:
5 On this side Jordan, in the land of Moab, began Moses to declare this law, saying,
6 The Lord our God spake unto us in Horeb, saying, Ye have dwelt long enough in this mount:
7 Turn you, and take your journey, and go to the mount of the Amorites, and unto all the places nigh thereunto, in the plain, in the hills, and in the vale, and in the south, and by the sea side, to the land of the Canaanites, and unto Lebanon, unto the great river, the river Euphrates.
8 Behold, I have set the land before you: go in and possess the land which the Lord sware unto your fathers, Abraham, Isaac, and Jacob, to give unto them and to their seed after them.
9 And I spake unto you at that time, saying, I am not able to bear you myself alone:
10 The Lord your God hath multiplied you, and, behold, ye are this day as the stars of heaven for multitude.
11 (The Lord God of your fathers make you a thousand times so many more as ye are, and bless you, as he hath promised you!)
I found it somewhat difficult to locate a good map of these descriptions. From those found searching google you see these. It appears that only in the years of David and Solmon did the kingdom appear to extend that far. Also note how large the Persian empire appeared, prior to shift of power to the west in Greece and Rome.
Hopefully the maps help, you can search for them under Google Deuteronomy 1 maps.