Rav Kook would sometimes speak about aschalta d'geulah. Several rabbonim from Hungary would attack him in their essays in the Hebrew newspapers, arguing that this notion doesn't make sense - either you have geulah or you don't have geulah - why did Rav Kook invent a new concept of aschalta d'geulah. The truth of the matter is that the expression “aschalta d'geulah” appears in the gemarah. The gemarah states that milchomos (wars) are an aschalta d'geulah. The Chasam Sofer wrote in his diary that there was a period of time that the city Pressburg was under siege in the middle of a war. The war had nothing to do with the Jews or with Eretz Yisroel, and nevertheless the Chasam Sofer understood the gemarah as saying that all wars in the world are aschalta d'geulah. He considered this idea as a halachic concept and said and wrote that one is not permitted to daven that the war should end because you are, in effect, slowing down the process of the geulah. One might have thought that only a navi or one who has ruach ha'kodesh could determine that any given situation is an aschalta d'geulah but the Chasam Sofer did not require such a condition.
Many years later during World War I a suggestion was made that the rabbonim should be gozer a ta'anis and everyone should daven that the war should end. The Minchas Elozer (Munkatcher Rebbe) dedicated a teshuva to this issue and gave two reasons why he was opposed to the idea: first, it only makes sense to declare a ta'anis tzibbur if there is a reasonable possibility that the tzibbur will do teshuva, and at that time that seemed highly unlikely. Second, he quoted from the Chasam Sofer's diary that all wars in the world are aschalta d'geulah and it is highly improper to slow down the process of geulah.
Rashi, in his commentary on the gemarah, does not seem to agree with the position of the Chasam Sofer. Rashi understood that a war regarding who is the ba'al ha'bayis of Eretz Yisroel which the Jews win would be considered an aschalta d'geulah. In order to determine what should be considered an aschalta d'geulah, we have to first establish what the definition of geulah is. The Ramban writes in his introduction to Sefer Shemos that Sefer Bereishis is all about the three beginnings: the beginning of the world, the beginning of mankind, and the beginning of the Jewish nation. By the end of Chumash Bereishis we have been introduced to the avos (Avrohom, Yitzchok, and Yaakov) and the twelve shevatim. Sefer Shemos then focuses on the first galus of the Jewish people, and the geulah therefrom. Then the Ramban raises an objection to this characterization: the Jewish people don't return back to Eretz Yisroel until after the death of Moshe Rabbeinu when they crossed over the Yarden river under the leadership of Yehoshua bin Nun; not only does the story of the Jewish people entering Eretz Yisroel not appear in Sefer Shemos, it does not appear in the Chumash at all! How can we describe the theme of Sefer Shemos by stating that it deals with the first galus and the geulah therefrom if the returning to Eretz Yisroel only takes place in Sefer Yehoshua? The Ramban explains that the main tragedy in galus Mitzrayim was not so much that the Jews were in chutz la'aretz but rather that they did not have any hashra'as haShechinah. During the lifetime of Avraham, Yitzchok and Yaakov the medrash states that the avos were like the merkava; they had a hashra'as haShechinah. By the time we get to the end of Sefer Shemos, we have read the four parshiyos of Teruma, Tezaveh, Vayakhel and Pekudei which all deal with the construction of the Mishkan, and the hashra'as haShechinah in the Mishkan is considered the geulah. It would appear that the Ramban understood that when the gemarah says that the first geulah took place in Nissan and the geulah asida will also take place in the month of Nissan, the first geulah being referred to is not Yetzias Mitzrayim, rather it is hakomas ha'Mishkan. During the first twelve days in the month of Nissan, the nesi'im of the twelve shevatim brought special korbanos for the purpose of chanukas ha'Mishkan, and in the end of Sefer Yechezkel we read that when the third Beis Hamikdash will be built we will bring special korbanos for a period of six and a half months, starting from Rosh Chodesh Nissan and continuing until after Sukkos.
When Medinas Yisroel was established in 1948, the Chazon Ish had already moved to Eretz Yisroel. In the biographies of the Chazon Ish it is quoted that he said at that time that this is the end of the galus but we still have not experienced the geulah. Many thought that this was some type of double talk. My impression is that the Chazon Ish is using the concepts that the Ramban developed: since you have a Jewish government controlling Eretz Yisroel all the Jews from all over the world were welcomed to come to Eretz Yisroel and that was considered the end of the galus. But one only has a geulah when you have a hashra'as haShechinah with a Beis Hamikdash.
Once we define geulah as binyan Beis Hamikdash, then aschalta d'geulah would refer to some other events that are going to lead up to the building of the Beis Hamikdash. The gemarah in Sanhedrin (20), quoted by the Rambam in the beginning of Hilchos Melachim, states that there are three mitzvos that have to be fulfilled in a specific order: establishing a Jewish government controlling all of Eretz Yisroel, wiping out the nation of Amalek, and building a beis ha'bechira (a.k.a. the Beis Hamikdash).
During the period of the second Beis Hamikdas, the chachomim added on many yomim tovim d'rabbonon that revolved about major donations to improving the structure of the Beis Hamikdash, the hakovas ha'korbonos, and the institutions of kehunah gedolah and sanhedrin, both of which are connected to the Beis Hamikdash. All of these yomim tovim are listed off in Megilas Taanis. Rashi in his commentary on the gemarah explains that this sefer was known as a megillah because it was already written down before the mishna and the gemarah were permitted to be written down. The gemarah in Rosh Hashanah states that it is not proper to establish a yom tov after the destruction of the Beis Hamikdash because it does not conform to the definition of Megilas Taanis. The commentaries on the gemarah therefore raise the issue: how did Chazal have the right in the first place to establish the yom tov of Purim? According to the gemarah's tradition, the story of Purim took place towards the end of the seventy years of galus Bavel when there was no Beis Hamikdash at all. According to the Pri Chodosh, establishing a yom tov that has nothing to do with the Beis Hamikdash would be a violation of bal tosif!
The Nesivos, in his commentary on Megilas Esther, suggests that the chachomim in that generation felt that on the occasion of neis Purim this was an aschalta d'geulah, i.e. that this would certainly lead to the building of the second Beis Hamikdash. Why so? He explains that Haman is described in the Book of Esther as an Amoleiki and when Haman and his whole crew were put to death, that was mechiyas Amalek, which is step #2 of the mitzvos that lead to the building of the Beis Hamikdash. Like the Chasam Sofer, the Nesivos also assumed that aschalta d'geulah is a halachic concept that carries with it halachic consequences.
Soon after hakomas ha'medinah the German government offered reparations money to the State of Israel. At that time, many members of the kenesset felt it to be unethical to accept such money because that would imply that the slaughter of the millions of Jews will all be forgiven by this payment. At that time, Rav Soloveitchik spoke for the Mizrachi in New York and brought out two points: 1. he would tend to agree with that position that we have no right to imply that all is forgiven, and 2. he heard from his father that any nation that adopts as a policy to wipe out the entire Jewish people has the status of Amalek and as such it should not be permissible to take the money from the German government; just as Shmuel Ha'navi instructed Shaul Ha'melech that he must not take anything from Amalek, so too throughout the generations one is not permitted to take anything from Amalek even if, for example, it is only a fraction of the money that the Nazis stole from the Jewish people. At that time, some of the relatives of Rav Soloveitchik who lived in Eretz Yisroel let it be known that they did not agree with Rav Soloveitchik. They pointed out that the Rambam in Moreh Nevuchim seems to assume that only those that are biological descendants, ben achar ben, from the original Amaleikim have the status of Amalek. When this position was publicized, some talmidei chachomin in America pointed out that Rav Yisroel Gustman had mentioned a conversation that he had with Rav Chaim Ozer in the middle of the Second World War. Rav Gustman asked Rav Chaim Ozer what the halachic status of the Nazis is, and Rav Chaim Ozer responded, that he would tend to agree with the other gedolim in that generation that the Nazis should probably be considered like Amalek.
In Parshas Beha'aloscho, the Torah instructs us that when there is a war in Eretz Yisroel we had a mitzvah to blow chatzotzros. The Rambam in the beginning of Hilchos Ta'aniyos understands that to mean that there is a special mitzvah lizok u'lihori'a, i.e. to offer special tefillos on the occasion. The Chasam Sofer in his diary wrote that during that war that he experienced in Presburg, they recited Avinu Malkeinu every day. Even on Chanukah, when we don't say Tachanun, we still ought to recite Avinu Malkeinu. On Rosh Hashanah we don't say Tachanun but we do say Avinu Malkeinu. Most probably the correct time to say Avinu Malkeinu after Shacharis should be right after chazoras ha'shatz and before Hallel. A talmid chochom from Lakewood pointed out that in the Siddur Otzer Hatifilos right before Avinu Malkeinu, appears an explanatory paragraph quoting several acharonim who point out that the entire Avinu Malkeinu is based on the nineteen berachos of the weekday shemone esrei. Let us all continue to offer our tefillos that Hakadosh Boruch Hu fulfill his promise that he will wipe out Amalek and that He strengthen the hands of Tzahal that they should be able to fulfill the mitzvah of wiping out Amalek and that this war should lead to the final geulah.