This is what I read from historical sources:
During WW2 one of the adages of the Previous Rebbe of Lubavitch (Rabbi YY Scneerson ztz”l) was “l’alter l’teshuvah, l’alter l’geulah” that immediate repentance would lead to immediate redemption. This was a claa for teshuva (kind of a kiruv/outreach program).
He also established cheders and sent rabbis throughout the heartland of America to cater to the needs of yidden in various cities that lacked chinuch and Torah leadership.
The outreach program of Chabad was called Merkos L’Inyonei Chinuch. He also turned his attention to be mikarev Jewish farmers – a popular career choice of Yidden in rural USA. Many of these programs were run by his son-in-law, before he became the past Rebbe.
Before leaving the USSR he gathered 10 Chassidim and made them give an oath that they will spread Judaism in Communist Russia till the last drop of blood. Many of them indeed were executed or died in prison al kiddush Hashem to keep the flame of yiddishkeit burning by setting up shchita, mikva, cheders, shuls, matza bakeries etc. The teshuva movement in the former USSR that we see today is the fruit of the seeds planted back them.
Upon Arriving in America he proclaimed “America is not different (than the Old Country)” – one CAN remain a frum yid in America. He then set out to facilitate this goal.
Facinating stuff went on in those days of the early kiruv movement in America – the treif medina..