We daven and hope that the war in Eretz Yisroel comes to a speedy end with the arrival of Moshiach and that we hear no more sirens throughout Eretz Yisroel. However, theoretically speaking, if a siren would go off during Succos, and everyone runs inside to the safe room/bomb shelter etc., would one be allowed to enter his succah and make a berachah of לישב בסוכה? Or would it be like sitting in a succah with branches hanging down within ten tefochim which is considered a dirah serucha (דירה סרוכה), an apartment to uncomfortable to live in (Succah 4a)?
R' Zilberstein (Chasukei Chemed, pg. 51) discusses this shailah. He says: It’s true that one is sitting in a place unfit for living in, however, there is a big difference between the dirah serucha of the Gemara in Succah and our case. In the case of the Gemara, the succah itself is unfit for living in, as branches are hanging down into the succah. In the case of a siren, however, the succah itself is fit for living in. There is kosher sechach serving as shade, and plenty of space, it’s just there is an external factor of fear which makes it unsuitable for living in, therefore, perhaps it’s better than the case of a dirah serucha. In short, perhaps an internal problem is worse than an external problem.
However...
However, the Rema (Orach Chaim 640:4) writes: “If one made a succah in a place where it’s uncomfortable to eat, drink, or sleep in, even if one can’t do just one of these things because he is afraid of intruders or bandits when in the succah – he can’t fulfil the mitzvah with such a succah, even when doing something he isn’t scared to do (i.e. if he is scared to sleep in the succah but isn’t scared to eat, he still can’t fulfil the mitzvah of eating in the succah) as it is not considered a place of living that one can do all his needs in.” We see from here, that even though the succah in and of itself is fit for living in, it is still considered a dira serucha (as is clear from the Biur HaGra s.k. 7 who compares this to a case where branches are sticking down into the succah below ten tefochim).
It All Depends on Bitachon
R’ Zilberstein suggests that whether one can stay in the succah and make a berachah or not depends on one’s level of bitachon in HaKodosh Boruch Hu. If one has a high level of bitachon and when he sits in the succah he fulfils: כי יצפננו בסכה ביום רעה - “Hashem hides me in His shade on a bad day”, then one may stay in the succah and make a berachah and he fulfils the mitzvah of succah.
If, however, one isn’t on such a high level and he is scared, then he can’t make the berachah of לישב בסוכה.
In the case of bandits, even if one says he isn’t scared it doesn’t help (see Mishnah Berurah s.k. 22) as in such a case there is a real danger. In our case of the siren, however, there is a very low chance that a rocket will actually hit the succah. It’s just that it’s the nature of people to be scared and run to a shelter. Therefore, if one overcomes this and puts his trust in the Ribbono Shel Olam, then perhaps he may stay in the succah and continue to fulfil the mitzvah of succah.
R’ Chaim Kanievsky Concurs
R’ Zilberstein brings that R’ Chaim Kanievsky agreed that the case of the siren is not the same as a succah in a place where there are bandits. In the case of bandits, the succah is never suitable as there is a constant danger. In the case of the siren, however, the succah is suitable to be used, and the siren going off is like a bandit entering the succah as a one-off, therefore, it doesn’t ruin the kashrus of the succah.
It’s said over about HaGaon HaTzaddik R’ Chaim Yaakov Roitenberg zt”l, who was a rav in Paris. That when he was in the camps with the Nazis (yemach shemom) he built a succah on erev Succos to be able to eat there on the first night of Succos, and as soon as he finished eating a kezayis he took down the succah, because of pikuach nefesh.
It's also known that during one of the wars in Eretz Yisroel, people ran in fear to the succah of the Steipler to get chizuk [encouragement] and when they were there, they felt that his succah was protecting them.
