CTRebbe: It is well known that R’ Moshe learned under R’ Isse Zalman Meltzer in Slutzk and under R’ Pesach Pruskin in Shklov and then in Amtsislav and considered R’ Pesach as his primary Rebbe.
(see Reb Moshe, Mesorah Publications (ArtScroll series) by Rabbi Shimon Finkelman).
In addition, where would we be without the Alter of Sladbodka in whose Yeshiva learned R’ Ahron Kotler, R’ Yaakov Kaminetzky, R’ Yitzchok Hutner, R’ Reuven Grozovsky, R’ Dovid Leibowitz, R’ Yaakov Ruderman.