May an observant surgeon perform elective surgeries during Nine Days? Does it make a difference if the patient is not Jewish?
Non-emergency surgery should be avoided during the 3 weeks (Kovetz MiBeit Levi, page 11, halacha 8). The Shulchan Aruch(551) advises against being involved in situations that might involve "sakana" (danger) during the 3 weeks (bain hemetzarim). The Sh. Aruch(551:18) further cautions against hitting a child during the 3 weeks (based on Midrash Shocher Tov). If hitting a child is considered a "sakana," a surgical operation certainly is (Sha'aray Halacha Uminhag, siman 226 cited in Nitei Gavriel, Bain Hemetzorim, Vol. 1, page 145).
Maharsham writes in Sefer Da'at Torah (551:18) that the concern regarding hitting children is only in a room that does not have a mezuzah. Rabbi Yitzchok Zilberstein writes in Sefer Torat Hayoledet (page 307) that a a woman who requires a C-section should try and postpone it for after bain hametzorim. If this is not feasable, there is no concern because "shomer mitzvah lo yedah davar ra". He then quotes the above Maharsham, that a mezuzah guards protects and saves and therefore if the operating room has a mezuzah, there would be no concern. At any rate, continues Rabbi Zilberstein, G-d will protect the mothers who fulfil the mitzvah of pirya verivya (procreation). Moreover, a shaliach mitzvah comes to no harm.
Rabbi Moshe Feinstein had a different approach. He permitted surgery during the 3 weeks up until the 9 days. He quotes the Shulchan Aruch that the prohibition against hitting a child during the three weeks is because "keter meriri sholait," the evil spirit has control. He says this only refers to hitting that causes suffering as occurs when one hits out of anger. However, hitting that is for the person's benefit and with his consent is not included in this prohibition. During the nine days, a time of misfortune, one should avoid surgery, if possible (Masoret Moshe, Vol. 1, page 170).
Rabbi Asher Weiss' yeshiva published a Sefer Darchei Hora'ah - Bain Hemetzorim. Rabbi Yosef Weingarten writes that it is preferable to postpone any elective surgery. The comparison to spanking a child may not be compelling. When a child is spanked, the desire is for divine intervention to help improve the child's behavior and the "meriri" (divine judgement) can now step in and cause harm. An operation, however, is performed to cure and not cause harm and should be permitted. He then quotes Rabbi Zilberstein and writes (quoting Shu"t Hitorerut Teshuva) that shomer mitzvah lo yeda davar ra.
So, regarding the surgeon, what should he do? Rabbi Feinstein presents a lenient view until the nine days. Rabbi Weingarten appears to be even more lenient. There is a principle - "Halacha rofefet beyadecha - pook chazi my ama davar." When one is unsure of the halacha, go out and see what people are doing. I perform surgery, and I am unaware of any observant doctor in my area who does not perform needed surgery during bain hametzorim.
May Hashem grant all of Klal Yisroel good health and may the time come when doctors can inform their patients, "You are in good shape, no treatment required."
R' Yitzchak Zilberstein taught in a lecture:
Elective surgery which can be postponed until after Tisha B'Av should not be done during the 9 days. Before that (during 3 weeks) it is ok to do it.
A Dr. who will lose his job if he refuses to do surgery then may perform the surgery even during the 9 days.
Since the reason for not performing surgery during the 9 days is because of ריע מזליה, and therefore it is not advisable for a Jewish surgeon to perform elective surgery even on a non Jew during that time, (if avoidable) because it may not be successful, and it may be detrimental for the Dr's reputation.