Mitzvas Yishuv Eretz Yisrael

The Ramban (Shikchas H'Asin L'Daas HaRamban in Sefer HaMitzvos of the Rambam) writes:

The fourth mitzvah [that the Rambam forgot to count] is that we are commanded to inherit the land that Hashem Yisbarach V'Yisaleh gave to our fathers Avraham, Yitzchak, and Yaakov and not to let it remain in the hands of others of the nations of the world or to destruction etc.

The question then is, why did the Rambam not count the mitzvah of yishuv eretz yisrael in minyan hamitzvos?

The Megillas Esther there answers the question as follows:

And it seems to me that the Rav didn't count it because the mitzvah of inheriting the land and settling it only applied in the days of Moshe, Yehoshua, and Dovid and all of the time that they weren't exiled from the land. But after the exile from their land the mitzvah does not apply for all generations until the time that Moshiach comes. For, on the contrary, we are commanded according to what it says in Kesuvos (111a) not to rebel against the nations of the world to go and conquer the land with force. And they prove this from the pasuk, "I made you swear the daughters of Jerusalem etc." and they darshened it that klal yisrael shouldn't ascend the wall.

The Avnei Nezer in Yoreh Deah Siman 454 brings this opinion of the Megillas Esther. He writes as follows:

And it is clear that the author of the Megillas Esther did not see the Sifri inside, only that which the Ramban quoted. Because the Sifri in Parshas Re'eh brings this episode and there it states clearly in the following language, "and they returned and came to their place and they said that settling Eretz Yisrael is equal to all the mitzvos"... thus the mitzvah is b'zman hazeh... and behold it was also hidden from the author of the Megillas Esther the words of the Rambam in Hilchos Avadim that even nowadays the servant can force his master to go up [to Eretz Yisrael]. And the essence of his words that the reason the Rambam doesn't count yeshivas Eretz Yisrael is because it isn't noheg bizman hazeh and is not a mitzvah l'doros is nothing. For if so, why does he count terumos and maasros and challah which don't apply nowadays? And even in the times of Ezra they were not in effect min hatorah according to the Rambam. And it is obvious that any mitzvah that is noheg in the days of moshiach is considered l'doros...

But the proper answer is... as far as yeshivas eretz yisrael that the mitzvah of hacharem tacharimem is in order that we should settle the land... therefore he did not count hacharem tacharimem and yeshivas eretz yisrael as two, and he counted only the mitzvah of hacharem tacharimem.

So, according to the Avnei Nezer the Rambam does, in fact, count yishuv eretz yisrael as a mitzvah included within the mitzvah of hacharem tacharimem.

Rav Ovadiah Yosef in Yechaveh Daas Vol. 3 Siman 69 also brings the opinion of the Megillas Esther. He disputes the opinion of the Megillas Esther based on the same Rambam in Hilchos Avadim that the Avnei Nezer quoted (Avadim 8: 8,9). He also brings another Rambam in Ishus 13:20 to prove the point:

כ] אמר האיש לעלות לארץ ישראל, והיא אינה רוצה--תצא שלא בכתובה; אמרה היא לעלות, והוא אינו רוצה--יוציא וייתן כתובה; והוא הדין לכל מקום מארץ ישראל, עם ירושלים: שהכול מעלין לארץ ישראל, ואין הכול מוציאין משם; והכול מעלין לירושלים, ואין הכול מוציאין משם

He then writes as follows:

The Acharonim have already discussed the words of the Megillas Esther mentioned above and they pushed his words aside with two hands. See the words of our master the Chida in Sefer Yair Ozen (Maareches 10:5), and the words of the gaon Rabbi Chaim Plagi in Shu"t Nishmas Kol Chai (YD 48). Also see Shu"t Neveh Shalom (siman 7) and Shu"t Avnei Nezer (YD 454) and Shu"t Chavalim B'niimim (2:132, 5:48) and Shu"t Dvar Yehoshua (2:71) and others.

The point of the Megillas Esther from the gemara in Kesuvos 111a, however, still remains. What do we do with the three oaths? Many Rabbanim in Europe understood this gemara to mean that it was, in fact, forbidden to resettle Eretz Yisrael until the times of Mashiach. (This opinion could be consistent with the understanding that the mitzvah of Yishuv Eretz Yisrael is "l'doros". As the Avnei Nezer stated, even mitzvos that are only going to be practiced in the times of mashiach can be counted in minyan hamitzvos.)

However, others disputed this conclusion based on a number of arguments. First, this gemara is not brought by the Rambam or the Shulchan Aruch. This would indicate that it is not halacha, but rather aggadata.

Further, Rav Hershel Schachter (see Journal of Halacha and Contemporary Society volume 8 on Yishuv Eretz Yisrael) cites several acharonim who had different interpretations of the gemara. For example he cites the Maharal's pshat as follows:

Maharal explains that G-d never actually administered an oath to the Jewish people; He merely told us that a return to Zion would be impractical because by the laws of nature such a return would not work out. Any attempt at return, then, is not forbidden, but discouraged as futile. Should an attempt succeed, it clearly has triumphed over nature and is not in defiance of G-d's will.

He also brings two additional arguments. First, some explain that the issur in the gemara in Kesuvos is only to take the land by force. However, the state of Israel was created with the allowance of the nations of the world (i.e. due to the Balfour Declaration etc.). Second, some point out that one of the oaths was administered to the nations of the world "not to be overzealous in persecuting the exiled Jews". Once the nations failed to uphold their end of the oath, we are no longer bound by ours.