The last paragraph in Parshat Ki Teitzei describes Amalek’s attack on the Jewish People in the desert. As a result we are commanded to never forget and to utterly wipe out the nation of Amalek. Abarbanel is bothered by the discrepancy between the description of the attack here and the original recounting of the battle in Parshat Beshalach. There it appears that the battle involved the Jewish nation as a whole, while in Ki Teitzei it appears that Amalek attacked only the weak stragglers who brought up the rear. Also, in Beshalach Moshe instructs Yehoshua to prepare an attack against Amalek, while in Ki Teitzei it appears that the battle was a sudden unprovoked attack by Amalek. Furthermore, in Ki Teitzei there is no mention of Yehoshua’s attack and there is no mention of his victory.
Abarbanel answers that there were actually two separate incidents. Ki Teitzei records the initial unprovoked attack by Amalek against the weakened, vulnerable part of the nation. In Beshalach the Torah is telling us that after this cowardly attack and immediate withdrawal Moshe instructs Yehoshua to take a small group of chosen men and retaliate, the result being the defeat of the Amalekites. Ki Teitzei only mentions the initial cowardly attack, to awaken us to the necessity of never forgetting this perfidious action and to focus on their utter destruction.
Amalek’s attack on Israel was unique in four different aspects. First of all, the Jews were not threatening Amalek’s territory, nor was Amalek extending its own territory or seeking material booty. Secondly, Amalek attacked without warning without informing the Jews of their intentions, not in accord with the custom amongst warring nations at that time. Thirdly, the cowardly nature of their attack showed that there was no purpose to their actions. Finally, the nature of the attack clearly demonstrated they had no fear of G-d. Their action was essentially an attack on G-d.
In order to dispel the notion that only G-d would take revenge against Amalek, the nation is told that since it is goal of Amalek to destroy the Jewish nation, it is the Jewish nation’s responsibility to destroy Amalek. Even when they have rested from the conquest of their enemies in the Land of Israel they cannot rest from their responsibility to destroy Amalek.
The admonition to never forget the nature of Amalek and our ultimate responsibility to destroy them extends to all times and all places, even when we are not in a position to challenge them. This is what is meant by “You shall wipe out the memory of Amalek from under the heaven — you shall never forget.” The expression “under the heaven” is a reference to our situation in exile anywhere on the globe. Even though we may not be in a position to literally wipe out Amalek we must never forget who they are and what they did.