The opening verses of Parashat Yitro tell of Yitro's arrival at Beneh Yisrael's camp. Yitro, Moshe's father-in-law, had been a pagan priest, but then recognized the truth of monotheism. He now took the next step, and joined Beneh Yisrael as they encamped at the foot of Mount Sinai.
Rashi comments that Yitro was motivated to join the nation upon hearing of two events: Keri'at Yam Suf (the splitting of the sea), and the war against Amalek.
It seems difficult to understand why the war with Amalek contributed to Yitro's decision. The splitting of the sea was, of course, an extraordinary miracle, an event that was heard throughout the ancient world and led all the nations to look at Beneh Yisrael with awe. It is understandable that this miracle inspired Yitro to come and join Beneh Yisrael. But how did the war against Amalek have this kind of effect? What about this event inspired Yitro?
One answer is that Yitro was struck by the drastic decline that Beneh Yisrael experienced from the event of Keri'at Yan Suf to the war against Amalek. The Sages teach that at the time of Keri'a Yam Suf, every member of the nation, even the most unlearned among them, reached a certain level of prophecy. The nation at that moment rose to the greatest heights. Just several weeks later, however, when they found themselves without water, their faith was shaken, and they started asking, "Is G-d in our midst or not?" (Shemot 17:7). It was in response to this lack of faith that Hashem led Amalek to attack Beneh Yisrael. Yitro saw how the people so quickly fell from the stature of prophets to the point where they could actually question whether Hashem was with them. This rapid decline is what prompted Yitro to join Beneh Yisrael. The Gemara teaches that Torah is the "antidote" to the Yeser Ha'ra (evil inclination). Sinful tendencies are part of the human condition; as long as a person is alive, he is going to tempted by some lure, by some human weakness, by one or several of the many negative traits with which people are created. And in order to withstand these inclinations, we need to immerse ourselves in Torah. Therefore, when Yitro saw how fast people are capable of falling, he made the decision to join Beneh Yisrael, so he can access the Torah, the "antidote" to the Yeser Ha'ra and protect himself from spiritual decline.
Rav Yosef Salant (Jerusalem, 1885-1981) offers a different explanation of Rashi's comment. He writes that after the miracle of the sea, many people throughout the world attributed this event to Moshe Rabbenu. Rather than recognize the existence of a single, omnipotent Creator, they instead concluded that Moshe was a superior sorcerer who succeeded in defeating the Egyptians through his magical prowess. Yitro, who was well-versed in all the various forms of ancient paganism, including sorcery, likewise suspected that it was Moshe who split the sea by lifting his staff over the water. Beneh Yisrael's miraculous victory against Amalek, however, was clearly not brought about by Moshe. At the time of the battle, Moshe stood at a distance, on a hill overlooking the battlefield. And when the people looked heavenward, they received Hashem's assistance and defeated the Amalekites. This event showed that the splitting of the sea was wrought not by Moshe, but by an all-powerful G-d, and this motivated Yitro to come join Beneh Yisrael.
There might also be a third interpretation.
In the Book of Debarim (25:18), Moshe describes Amalek's attack with the word "Karecha." The Sages explained this term as a derivative of the word "Kar" – "cool." After the miracle of the sea, Beneh Yisrael were feared throughout the world. The Rabbis drew a comparison to a tub filled with scalding hot water, that nobody dared touch. When Amalek launched their attack, they were like a person who jumped into the tub of boiling hot water – he suffered bad burns, but cooled the water for anyone else who wished to bathe afterward. Amalek was defeated, but this battle had the effect of "cooling" Beneh Yisrael, of exposing their vulnerability. Beneh Yisrael now appeared far less fearsome, and no longer seemed invincible.
Yitro saw the grave Hillul Hashem – defamation of Hashem's Name – caused by Amalek's attack. The awe and admiration that the world felt toward Beneh Yisrael after the splitting of the sea were now gone. And Yitro understood that the only way to rectify a Hillul Hashem is by creating a Kiddush Hashem – a glorification of Hashem's Name. He therefore decided to join Beneh Yisrael. As a respected and wealthy public figure, his arrival would "make the news," and become widely known. People all over would hear that a prominent former pagan cleric had recognized the truth of the Jewish faith and decided to join Beneh Yisrael's ranks. This would repair, at least somewhat, the damage caused by Amalek's attack. And thus Yitro's decision was driven by these two events – the splitting of the sea and Amalek's attack, as he sought to restore the respect for Beneh Yisrael that was achieved by the miracle of Keri'at Yam Suf.
