Final answer:
St. Patrick was taken to Ireland as a slave at the age of sixteen, which is how he first came to know the land. After escaping and returning to Britain, he received a religious education and felt called to evangelize, leading to his return to Ireland as a missionary.
Step-by-step explanation:
St. Patrick first came to know the land he would eventually evangelize through a less than fortunate event. He was not a volunteer missionary but was brought to Ireland as a captive. At the age of sixteen, he was kidnapped by Irish raiders from his home in Britain and taken to Ireland to work as a slave. It was during this time in captivity, tending sheep and cattle, that he became deeply committed to Christianity and evangelization. After six years, he escaped and returned to his family in Britain, where he received a religious education. Feeling called to spread the Christian faith, he later returned as a missionary to the very land where he had once been held captive.