In 1943, the Union of Grand Rabbis and Agudas HaRabbonim issued the following plea calling on all rabbis to attend the Rabbis March on Washington. In part, it reads:
The Union of Grand Rabbis, as well as the Union of Orthodox Rabbis, appeals to support the action of the Emergency Committee to Save the Jewish People of Europe as a Redemption of Captives [pidyon sh'vuim]. It is important for the aim of rescuing the remnant of Israel in Europe that all Rabbis be present in Washington to add weight to the manifestation of the Rabbis, the Grand Rabbis and the leaders.
As mentioned in an earlier post, it seems that no senior Chabad rabbis from the Lubavitch community of Crown Heights attended.
The Rebbe and his brother-in-law the Rashag did not attend. The Freidiker Rebbe also did not attend. (While it must be assumed that the Freidiker Rebbe's illness prevented his attendance, it did not prevent him from sending representatives of note. Yet he did not do so.)
Now, let's look at the 1983 letter from the Ad Hoc Rabbinic Committee to Save Ethiopian Jews. It calls for support for House Resolution 107 (Senate Concurrent Resolution 55), asks that petitions that do so be circulated in synagogues, and includes an ad placed by the above-mentioned Emergency Committee to Save the Jewish People of Europe in the New York Times on February 16, 1943.
The Ad Hoc Committee's letter is signed by Reform, Conservative and Orthodox rabbis, including Rav Moshe Feinstein, Rav Yosef Ber Soleveitchick Rosh Yeshiva of Yeshiva University, Rabbi Norman Lamm, President of Yeshiva University, and Rabbi Marvin Hier of the Simon Wiesenthal Center.
There were no Lubavitch signatories. Chabad did not support the House Resolution. In the Rebbe's letter on the rescue of Ethiopian Jews, he ridicules US Government involvement in rescue and refuses to support the House Resolution because such support is not in the job description of Lubavitch.
The 1943 Rabbis March led to the rescue of 250,000 Jews from the Nazis. The 1983 Letter led to US backing for and involvement in the rescues that saved more than 25,000 Ethiopian Jews.