When was the prophecy of restoring the land fulfilled?

Answer:

"So it shall be when all of these things have come upon you, the blessing and the curse which I have set before you, and you call them to mind in all nations where the LORD your God has banished you, and you return to the LORD your God and obey Him with all your heart and soul according to all that I command you today, you and your sons, then the LORD your God will restore you from captivity, and have compassion on you, and will gather you again from all the peoples where the LORD your God has scattered you. If your outcasts are at the ends of the earth, from there the LORD your God will gather you, and from there He will bring you back. The LORD your God will bring you into the land which your fathers possessed, and you shall possess it; and He will prosper you and multiply you more than your fathers" (Deuteronomy 30:1-5).

After promising that God would uproot Israel from the promised land if they broke the covenant (Deuteronomy 29:24-28), God promised, through Moses, that He would bring them back to their land.

Israel did break the covenant, and Ezekiel prophesied at the start of the exile: "Therefore thus says the Lord GOD, 'Now I will restore the fortunes of Jacob and have mercy on the whole house of Israel; and I will be jealous for My holy name. They will forget their disgrace and all their treachery which they perpetrated against Me, when they live securely on their own land with no one to make them afraid. When I bring them back from the peoples and gather them from the lands of their enemies, then I shall be sanctified through them in the sight of the many nations. Then they will know that I am the LORD their God because I made them go into exile among the nations, and then gathered them again to their own land; and I will leave none of them there any longer. I will not hide My face from them any longer, for I will have poured out My Spirit on the house of Israel,' declares the Lord GOD" (Ezekiel 39:25-29).

These prophecies were fulfilled during the days of Ezra and Nehemiah. In fact, Nehemiah cites Moses' prophecy in his prayer to God. "Remember the word which You commanded Your servant Moses, saying, 'If you are unfaithful I will scatter you among the peoples; but if you return to Me and keep My commandments and do them, though those of you who have been scattered were in the most remote part of the heavens, I will gather them from there and will bring them to the place where I have chosen to cause My name to dwell'" (Nehemiah 1:8-9).

However, take note that God offered them a return if they returned to God and kept His commandments. While God did bring them back to the land, the people still didn't fully give themselves over to obeying God.