I was recently learning the 9th perek of berachos and the first sugyah is about making a beracha in the place where a neis happens. The halacha is (siman 218) that besides making a beracha on a neis that happened to klal yisroel (for example making a beracha by the yam suf), there are other situations that one would make a beracha.
1) Based on the Yerushalmi, we pasken that you make a beracha on a neis that happens to an adam chashuv like Yoav ben Tzruyah. The question is why. The Biur Halacha quotes the Elyah Rabba that someone like Yoav ben Tzruyah was the shaliach for all of klal yisroel. When a neis happened to him it was really a nes for klal yisroel and it is considered a nes shel rabim. B'zman hazeh we assume no such person exists and we don't make a beracha.
2) The Avudraham writes that we only make a beracha on an event that happend al pi nes. If it happened b'minhag ha'olom you don't make a beracha. He asks why do we make a beracha "sh'asa nisim" by Purim and Chanukah. He answers that Purim was a nes because the king went against the laws of the land and also he killed 80,000 people to please Esther. This is not monhag haolam and is a neis. Chanukah we only make the beracha over the nes of the oil and not the war.
This Avudraham is also interesting for a different reason. Some achronim (ayin Kuntres Chanuka U'Megillah) discuss whether the beracha of shasa nisim by Chanuka is a birchas hamitzvah or birchas hashevach. The Avudraham clearly takes the tzad that it is a birchas hashevach.
3) An individual wil also make a beracha at the place where a nes happened to him that saved him from harm. There are 2 opinions in the Shulchan Aruch whether the event that happend has to be through a real nes. It seems to me that there is a machlokes between the Mishna Berurah and Chayei Adam (siman 65 in Nishmas Adam), how to understand the opinion that one doesn't need a nes.
The Chayei Adam brings several proofs that we don't require that a person is saved through a nes but as long as he was saved "b'derech nes" he can make the beracha. For example, if a wall falls on a person and he really should have died but someone saves him so he wasn't saved through a nes but the fact that someone came and saved him was hashgacha pratis and it is "b'derech nes".
However, the Mishna Berura in the Biur Halcha learns a little differently. Both opinions in the Shulchan Aruch require that a person be saved through a nes. They only disagree what level of nes is m'chayeiv a beracha. The first opinion holds you need a real nes that is supernatural. The second opinion holds that even the fact that Hashem caused circumstances to happen to allow you to be saved is a nes. If robbers held you uyp and it just so happened that someone came by and saved your life-even though nothing supernatural happeend, that is a nes and since it is a nes you can make the beracha.
Although it seems like the Chayei Adam and Mishna Berura are saying the same thing, Ithink they are not. The Chayei Adam seems to be saying you don't need to define the event as a nes-as long as it happened in a way which we see yad Hashem and is b'derech nes, you can make the beracha. The Mishna Berura seems to be saying you must define the event as a nes.
I would like to add that perhaps they are arguing in the following chakirah. When we make a beracha at the yam suf that is clearly a beracha recognizing the fact that Hashem performed a nes for klal yisroel. How about when an individual makes a beracha on his personal nes? Is this also a shevach in recognition of the nes Hashem did or maybe it is a form of birchas hagomel. A regular birchas hagomel is thanking Hashem for saving you. Chzal were m'sakein that when Hashem saved you b'derech nes that you make a sh'asa nisim as well (when you pass by the place). It could be the Mishna Berura holds like the first tzad-it is only a beracha on a nes therefore you can only make the beracha if the event is defined as a nes. The Chayei Adam holds like the 2nd tzad, it is a unique form of birchas hagomeil and we don't care if the event that happened can be defined as a nes but rather did Hashem save you b'derech nes.
I have a few other nafka minas in this chakirah.
a) The Rivash writes that besides making a sh'asa nisim over an individual event, you also bentch gomel. His reasoning is based on a kal v'chomer, if I make a sh'asa nisim kal v'chomer I should bentch gomel. If Sheasa nisim is just a shevach in recognition for a nes Hahsem performed, what is the kal v'cho,er to gomeil-they are 2 distinct types of berachos. But if we say sh'asa nisim is a differeent form of gomeil the kal v'chomer makes sense.
b) There is a machlokes who makes this sh'asa nisim. Is it only the person's children and grandchildren or every generation. If the beracha is just a shevach over the nes so we can say all future generations make it-just like the beracha on the yam suf. But if it is a gomeil type beracha so maybe it is limite dto children and grandchildren since they benefit more directly than other descendents from the hatzalah so they can make the gomeil.