I do not understand all those who are saying that kiruv in chassidus goes back to the BeSHT or at least the beginning of Chabad chasiddus. There is a big difference between saying “kiruv is a good thing” which just about all Jews agree (BTW- even the non-Orthodox say this) and actively working towards it as a movement.
Correct me if someone has information to contrary but in Chabad the movement toward kiruv did not start until the last Rebbe. It is true that many individuals were moser nefesh to fight the communists under the direction of the previous Rebbe and did start schools but that can not be called a kiruv movement.
Kiruv as a movement in the Litvishe world was active before WW2 with Novardok and after the war in the later 1960’s with Yeshivos like Aish hatorah and Ohr Somayach