While in Shmos, Perek 17, the Torah sufficed with saying merely that Amalek came and attacked, here, in Devarim, the Torah elaborates on how Amalek ambushed the Israelites when they were weakened and weary from their journey. Does this action of Amalek betray a moral failing and thus explain the need to exact retribution from them, or does it simply reflect their use of sound military strategy? This question may depend, in part, on whether the accompanying phrase "וְׂלֹא יָרֵא אֱלֹהִּים" describes the character of the Israelites or the Amalekites.
Additionally, while Shemot 17 tells of HaShem's vow that He will be the one to destroy Amalek, in Devarim, it is the Children of Israel who are instructed to do so. What accounts for this discrepancy?
Timing of the Fulfillment
Devarim 25 commands that the eradicating of Amalek should take place only after the Israelites have completed the conquest of all of their other enemies. Shemot 17:16 even hints at an eternal battle with Amalek ("מִּלְׂחָמָה לַה' בַעֲמָלֵק מִּדֹר דֹר"). But if Amalek's crime was so heinous, why did HaShem postpone their day of reckoning? Could He not have ordered Moshe to wipe them out completely when Amalek first attacked in Shemot 17? Furthermore, why does HaShem tell Moshe already in Shemot 17 (before it is even known that Moshe will not be leading the nation into the Promised Land) to convey HaShem's intentions to Yehoshua? Is it not Shaul in Shemuel I 15, rather than Yehoshua, who is ultimately commanded to execute this command?
Approaches to Understanding from the Commentators
Immoral Conduct
Many commentators view the command to annihilate Amalek as a singular one which resulted from the gravity of their sin. This group highlights the immoral conduct of Amalek (בין אדם לחברו) in preying on the weak and defenseless. Amalek attacked without just cause and in an unscrupulous fashion. They are punished more harshly than other enemies of Israel because of their terrorist mindset and lack of moral norms. These commentators include Rabbi Yosef Bechor Shor, Abarbanel, Shadal, Rabbi Shimshon Raphael Hirsch and Rabbi Dovid Tzvi Hoffman.
Disrespect for the Divine
These commentators emphasize Amalek's defiance of HaShem (בין אדם למקום). Whereas the miracles of the Exodus generally achieved their goal of having all of the nations recognize HaShem and tremble before Him, Amalek had no such fear but rather desired to profane HaShem's name. In eliminating the Amalekites, HaShem turned them into an example from which the rest of the world would learn.
Existential Threat
Another group, though, understand that neither the Amalekites' actions nor their punishment were so extraordinary or reflect a particularly grievous interpersonal or religious sin. The Amalekites desired to completely exterminate Israel. Thus, wiping them out was the only way to eliminate their ongoing threat to the Israelites' survival. Thus, they focus instead on the potential danger which Amalek's existence posed to the security and survival of the Children of Israel. These are the view are the view of Ralbag and Umberto Cassuto.
No Different than the Others
Finally, the Mechilta appears to go a step further in viewing the destruction of Amalek as merely the prototype for the standard fate of all enemies who dare to attack Israel. Neither Amalek's actions nor their punishment was exceptional. Throughout Tanach, enemies of Israel are annihilated either by the direct hand of HaShem or in battle with Israelite armies.
Contrasting the Differing Opinions
Immoral ConductDisrespect for the DivineExistential ThreatNo Different from the Other Nationsוְלֹא יָרֵא אֱלֹהִיםAnd they did not fear G-d
This phrase describes Amalek. Either they had no fear of G-d or no moral or ethical norm. The subject is Amalek. HaShem is pointing to the negative of Amalek’s actions that they do not fear G-d.The phrase refers to the Israelites, who, at the time of the initial attack, were not yet infused with a fear of G-d. Refers to the Jews who were not sufficiently fearful of G-d and lack of observance paved the way for the attack.Amalek had no good reason for attacking, as it was neither a war of defense nor conquest for them, nor was there any provocation on the part of Israel.Amalek has nothing to gain from the attack and fought only to denigrate the name of G-d by attempting to show they were more powerful than G-d.Associated with the blessing given to Esav to be ruled by Yaacov. Amalek attempted to kill off the Jews and avoid future servitude.The attack was a response to the Jews’ sins and laxity in observing the Torah. Amalek was a Divine “agent” to punish and educate the Jews.וַיְזַנֵב בְךָ כׇּל הַנֶּחֱשָלִים
Amalek cut off all the weak
Amalek’s preying on the weak is what underscores their immorality.A simply military action to attack from the rear. Israel’s apparent weakness was a main motivation to attack. History shows such a pattern of attack by Amalek when the Jews were weak.The actions of Amalek were not immoral but were merely strategies of war.HaShem or Israel is active
Both play a role in the destruction of Amalek as their attached was aimed at both. If the Jews do their job, HaShem would assist.Jews were to act as of agents of G-d.Yehoshua’s future role
Since he was the leader in the original battle he was given the honor to knowing that the job would be completed.Yehoshua was instructed only in the th year when he was designated as the next leader and was the right party to command.The leadership in the current war hinted to the future leadership position for Yehoshua.When to destroy
HaShem commanded to destroy Amalek only after settlement of Eretz Yisrael.HaShem wanted the 7 nations to first be destroyed and then to annihilate Amalek.The Jews needed to delay until they were capable of destroying Amalek.מִדֹר דֹר
From generation to generation
In the ongoing war against the idea that “might makes right”, HaShem reminds us not to forget we are antithesis of AmalekThe eternal battle is against their belief system which denies the concept of Divine Providence.The obligation extents as long as Amalek continues to pose a threat.
See alhatorah.com for a more complete analysis.