Lest we forget, or become confused about the issue, the greatest missionary of all times was without a doubt Jesus Christ.
Missionaries face a variety of barriers on the field.
Among the first to be overcome is immigrations. It is often difficult to establish a right to reside with the people we want to minister to. Jesus overcame that barrier. He became part of the group he wanted to minister to. He laid aside the rights and privleges he had as a citizen of Heaven and became a citizen of Earth.