In its “Memorial Day Law,” the Knesset determined that the day before Yom HaAtzmaut will be “A memorial day for the soldiers of the Israel Defense Forces (IDF or Tzahal), who gave their lives to ensure the continued existence of the State of Israel, and for those who fought and fell in the campaigns to create the State of Israel – to memorialize them and pay tribute to their courage.” “Memorial services, public gatherings, and ceremonies will be held on army bases and in educational institutions. Flags will be lowered to half-mast on public buildings.” In addition, the Knesset decided that “Two minutes of silence will be observed throughout the country, during which all work and travel will cease.” To facilitate the two minutes of silence, a siren wails throughout the country, and people stand still in honor of the fallen. In practice, at 8:00 p.m. Yom HaZikaron evening, the siren sounds for one minute, and at 11:00 a.m., the next morning, it wails for two minutes, during which time everyone dedicates his or her thoughts to the memory of the fallen. The official ceremonies begin immediately thereafter.
Some claim that it is forbidden to stand at attention when the siren blasts, because this custom has no basis in rabbinic literature. Rather, we copied it from the Gentiles, and one may not follow the ways of the nations, as it says, “Do not follow their ordinances”(Vayikra, 18:3). In practice, however, the vast majority of poskim hold that the prohibition against following the ways of the Gentiles applies only when one of two conditions is met: 1) the custom entails a breach of modesty or humility, 2) it has no apparent reason or benefit, making it clear that it is based on a vain heathen belief (Maharik,Shoresh 88; Rivash 158). Rabbi Yosef Cairo and the Rama concur (Beit Yosef and Haga, Yoreh Deah 178:1). Thus, since the custom under discussion has a purpose – by way of the siren and standing silently, everyone unites together to remember the fallen – it is not considered a gentile practice13.
Others claim that one should not interrupt Torah study on account of the siren. However, our teacher, HaRav Tzvi Yehuda HaKohen Kook, zt”l, writes, “Standing silently for the fallen soldiers of Tzahal contains within it the holy mitzvah of remembering the glory of the holy ones.” Moreover, it is possible to say that meditating upon the memory of the holy soldiers and the mitzvah to sacrifice one’s life to save the nation and conquer the Land is tantamount to thinking Torah thoughts. And even those who do not understand this must be mindful of Hillel the Elder’s teaching: “Do not separate from the community” (Avot 2:4)14.
 Indeed, the Vilna Gaon opines that we may not imitate the nations even with regard to a custom that has a rationale behind it. He, therefore, prohibits placing branches in a synagogue on the holiday of Shavuot, because the heathens put trees in their houses of worship on their holidays (Chayei Adam 131:13; see Biur HaGra, Yoreh Deah 178:7). Practically speaking, though, most poskim disagree with him and uphold the custom of decorating the synagogue on Shavuot, as the Rama (O.C. 494:3) and Magen Avraham (ibid. 494:5) write: since there are reasons for this custom, it is not considered following the ordinances of the nations. Now, if that is what they say about the custom of placing branches in a synagogue, which is actually done in houses of idol worship, there is certainly nothing to worry about with regard to the custom of standing silently at the sounding of the siren, which has no hint of idolatry whatsoever. Furthermore, I have been told that this custom is almost unheard of amongst the Gentiles.
 Pesikta Zutrata (Lekach Tov) on Shemot 2:11, states: “It came to pass in those days that Moshe grew up and went out… He went out to see the suffering of Israel. This is what Hillel taught, ‘Do not separate from the community.’ If a person sees the community in pain, he should not say, ‘I will go to my house, eat and drink, and all will be well with me.’ Rather, one should bear the burden with his fellow Jews.” Midrash Seichel Tov on the same verse adds: “This is what Hillel taught, ‘Do not separate yourself from the community.’ Our Rabbis taught, ‘If the community is in pain and someone separates from them and eats and drinks, two ministering angels accompany him, place food on his head, and say, ‘So-and-so separated himself from the community in their time of trouble; he shall not see the community’s consolation.’ The Rabbis further taught: ‘When the community is in pain, a person should not say, “I will go to my house, eat and drink, and all will be well with me.” And if he did so, the verse says about him, ‘Behold, joy and gladness, slaying cattle and slaughtering sheep, eating meat and drinking wine; eat and drink, for tomorrow we shall die’ (Yeshayah 22:13). What is written afterwards? It was revealed in my ears by the Lord of Hosts, that you will not be atoned for this sin until you die.’ ”
Rav Tzvi Yehuda Kook’s words are quoted in Techumin, vol. 3, p. 388. See also Rabbi Ariel’s Responsa Ohalah Shel Torah, Yoreh Deah 23. Rabbi Chayim David HaLevi writes in Asei Lecha Rav (4:4) that one who is involved in Torah study at home should continue learning, for standing silently is illusionary honor, which one must practice only when others are watching. He adds that in public, one may stand and continue thinking about the topic he was studying. Rabbi Henkin concurs in Techumin, vol. 4, p. 125. However, I believe that what I wrote above is correct, for contemplating the mitzvah of Kiddush Hashem (sanctifying God’s Name) is itself considered meditating on Torah, and it is preferable to include oneself in the community with holy thoughts.