Following this line of reasoning, we will now explain the fascinating relationship between the battle with Amalek and the miracle of Purim. Toward the end of the Megillah, we find an oddity in the text (Esther 10, 1): "וישם המלך אחשורוש מס על הארץ ואיי הים"—King Achashveirosh levied a tax on the mainland and the islands of the sea. Tradition teaches us that the name "אחשורוש" in this passuk is read with two “vavs,” although it is written as "אחשרש"—without the two “vavs.” There must be a reason for the omission of these two “vavs.”
I believe that we can explain the reason based on what the Gaon Chida presents in Midbar Kedeimos (40, 25) in the name of the sefer Archei HaKinuyim, authored by the divine kabbalist, the Ramaz, Rabbi Moshe Zachuta, ztz”l: "מרדכי הוא גלגול יעקב והמן הוא גלגול עשו"—Mordechai was a gilgul of Yaakov; and Haman was a gilgul of Eisav. Accordingly, Amalek was the grandson of Eisav; his people waged war against Yisrael to take away from them the two “vavs” of "דור דור". As mentioned, Yisrael inherited them from Yaakov Avinu, who completed the process of the two “vavs.” Similarly, Haman, all of his advisors, and his wife, who were descendants of Amalek, fought to take away these two “vavs” from Yisrael in the times of Mordechai, who was a gilgul of Yaakov.
Based on what we have learned, we can begin to comprehend the strategy suggested to Haman by his wife and his advisors (ibid. 5, 14): "ותאמר לו זרש אשתו וכל אוהביו יעשו עץ גבוה חמישים אמה ובבוקר אמור למלך ויתלו את מרדכי עליו." So his wife, Zeresh, as well as all his friends, said to him, “Let them make a gallows, fifty cubits high; and, in the morning, speak to the king and have them hang Mordechai on it.” According to the Arizal (Eitz Chaim 25, 2), a final “nun”— ן' – is made up of two “vavs” one on top of the other; when connected they form an elongated, final “nun.” Thus, the plan was to hang Mordechai on a tree fifty (the numerical value of “nun”) cubits high to prevent him from perpetuating the study of Torah “from generation to generation”— "מדור לדור"—which is based on these two “vavs.”
Now, Chazal (Megillah 14a) attest to the fact that Achashveirosh was every bit as wicked as Haman; in fact, he originally sanctioned Haman’s plan and was complicit in his malice. Therefore, the name "אחשורוש" is written with the two “vavs” that were stolen from the realm of kedushah. As we know, Mordechai and Esther ultimately prevailed, and Haman and his ten sons were hung on the same fifty-cubit high tree that Haman had prepared for Mordechai. Thus, they took control of the two “vavs” that Amalek and its descendants wanted to steal from the realm of kedushah, as reflected by the spelling of "מדר דר". Since Achashveirosh miraculously consented to have Haman hung on the tree (comprised of two “vavs”), Mordechai and Esther were able to also remove the two “vavs” from his name. Hence, at the end of the Megillah, it is spelled "אחשרש".
This explains beautifully the following text in the Megillah (ibid. 9, 28): "והימים האלה נזכרים ונעשים בכל 'דור ודור' משפחה ומשפחה מדינה ומדינה ועיר ועיר וימי הפורים האלה לא יעברו מתוך היהודים וזכרם לא יסוף מזרעם". And these days should be remembered and celebrated by every generation, every family, every province, and every city; and these days of Purim should never cease among the Jews, nor shall their remembrance perish from their descendants. Note that "בכל דור ודור" is written in its full form with both “vavs”; this indicates that they successfully took back the two “vavs” that Amalek stole from the realm of kedushah. Therefore, the passuk concludes: “And these days of Purim should never cease among the Jews, nor shall their remembrance perish from their descendants.” For, just like Yaakov Avinu, the third of the Avos, paved the way; so, too, did his gilgul after him, Mordechai, pave the way for this dictum to take effect: Anyone who is a Torah scholar, and whose son is a Torah scholar, and whose grandson is a Torah scholar, the Torah will never again cease from his descendants.
Lastly, it behooves us to point out that the Anshei Kenesses HaGedolah, the authors of the Megillah, chose to begin the Megillah with the letter “vav”: "ויהי בימי אחשורוש"; and they also chose to end the Megillah—praising Mordechai—with the letter “vav”: "דורש טוב לעמו ודובר שלום לכל זרע'ו". We can suggest that they did this to allude to the miracle of Purim—the success of Mordechai and Esther in extracting the two “vavs” from Haman, the descendant of Amalek, and also from the name of "אחשורוש". Thus, they succeeded in extending the tradition of the Torah to all of their descendants "דור ודור" –in all future generations via two intact “vavs”—the fulfillment of the concealed tefilah we recite thrice daily: "לדור ודור נודה לך ונספר תהילתך"—in Modim.
This also explains very nicely why they instituted saying Ahl HaNissim for the miracles of Chanukah and Purim in the berachah of Modim. As explained, Modim contains a concealed tefilah for the perpetual existence of the Torah: "לדוד ודור נודה לך ונספר תהילתך". The miracle of Chanukah involved the Greeks attempting to make the Jews forget and forsake the Torah. Similarly, the miracle of Purim involved Haman, the descendant of Amalek, attempting to eliminate the two “vavs” of "דור דור". Therefore, Modim is the appropriate place to recite Ahl HaNissim.
