Jesus told his disciples that he will return only once and that when he does, after a time of great tribulation, it will be visible to everyone and be followed by immediate and dire consequences for those unprepared and for those who were adversaries of God.
All Christians are commissioned and obligated to be evangelizers wherever they are, in that they preach the good news to all sorts of men.
Always there have been real followers of Jesus who only worshipped his One God, the God of Israel. Many centuries they worked and preached behind closed doors, avoiding persecution and death on the balefire. In fear of the stake for centuries the real followers of God baptised people in their faith, not demanding to be part of one or another church but being part of the Body of Christ.