The transfer of the Land of Israel to the Jewish people has not yet reached its perfection.
Indeed, even at its peak, as in the times of King David and King Solomon, the Jewish people only occupied the “lands of the Seven Nations” and had not yet received the “the Lands of the Ten Nations”.
The lands of the Knanyans, Knizians and Kadmonians, which are an integral part of the territory that God promised Abraham, have never been in our possession.
This will take place only after the onset of the Redemption, when all the dead will be revived and all the Jews from all the generations will live on our land. At that time, the borders of the Land of Israel will also be expanded to include the lands of the ten nations.
Hence it is clear that the connection of the Jews with the Holy Land has not yet been completed in its entirety. Jews have not yet united with the Land. This will happen only in the future, but for now the directive "Go ... to the land that I will show you" has not yet been fulfilled.
We are currently at the end of this process which should be completed in the very near future. Thus we are required to prepare ourselves for the perfect possession of the Land of Israel. This training is called “the mind controlling the emotions” which amounts to engaging the three powers of reasoning - mind, understanding and knowledge (CHABAD) - that correspond to the spiritual aspect of the three lands that will be added to the Land of Israel.
With this, the prayers of "gathering the Jewish people scattered around the world" will be fulfilled in the literal sense of the word.
Everyone is wondering where these three lands of the Kenyans, Knizians and Kadmonians are. The Jerusalem Talmud contains a controversy on this subject:
“Rabbi Yehuda says that these are Arabia, Salmiya and Nabatiya. Rabbi Shimon believes that these are Asia, Spain and Damascus. Rabbi Eliezer, son of Yaakov, believes that these are Asia, Carthage and Turkey. And according to the Rabbi, these are Edom, Moab and the beginning of Ammon. "
In any case, says Rebbe, King Moshiach, during the Redemption, the peoples of the world themselves will give all these lands to the Jews and there will be no need to fight for this.