There is a story that says that many years later, he heard in a vision the voice of Ireland asking him to return to them. (The story is strangely reminiscent of the voice that Paul heard asking him to come to Macedonia, (Acts 16:9.)) As the story goes, Patrick did return to Ireland. Upon his return he was met with resistance from the Druids. His new faith in God was apparently seen as a frontal assault on their religious hegemony in Ireland. That is the background for what has become known as Patrick's Lorica, or Breastplate. One source explains:
"Saint Patrick and his companion missionaries were to travel to the court of King Laoghhaire. Along the way, waiting in ambush, were druid or druid henchmen who intended to attack and kill Saint Patrick and all his followers.Whether you believe that this actually took place isn't important. What is important is that this humble man dedicated his life to his God first, then to his enemy. He trusted in Yahweh as Father, Son and Holy Spirit.
As Patrick and his companions walked, they chanted the Lorica. When they passed the would-be attackers, they appeared as a doe and twenty fawns."
I blogged awhile ago on the lorica. Here is a link to that post.