Ireland is unique in religious history for being the only land into which Christianity was introduced without bloodshed. There are no Irish martyrs (at least not till Elizabeth I began to create them eleven centuries after Patrick). And this lack of martyrdom troubled the Irish, to whom a glorious death by violence presented such an exciting finale. If all Ireland had received Christianity without a fight, the Irish would just have to think up some new form of martyrdom- something even more interesting than the wonderfully grisly stories they had begun to learn in the simple continental collections, called "martyrologies," from which Patrick and his successors taught them to read.
The Irish of the late fifth and early sixth centuries soon found a solution, which they called the Green Martyrdom, opposing it to the conventional Red Martyrdom by blood. The Green Martyrs were those who, leaving behind the comforts and pleasures of ordinary human society, retreated to the woods, or to the mountaintop, or to a lonely island- to one of the green no-man's-lands outside tribal jurisdictions- there to study the scriptures and commune with God. For among the story collections Patrick gave them they found the examples of the anchorites of the Egyptian desert, who, also lacking the purification rite of persecution, had lately devised a new form of holiness by living alone in isolated hermitages, braving all kinds of physical and psychological fasts and penances, all for the sake of drawing nearer to God.
from page 151, How the Irish Saved Civilization