This book examines the involvement of the Irish Catholic Church since 1830 in evangelizing peoples and countries where the Gospel had not previously been preached. However, the book does not deal with apostolic outreach to Irish emigrants or to predominantly Christian countries. The modern missionary movement was a product of the institutional revival of Irish Catholicism from the 1840s onward. Continental missionary agencies visited Ireland from the late 1830s on and encouraged its development. The growing self-confidence of Irish Catholicism, most of whose domestic difficulties had been resolved by the late 19th-century, caused it to project its energies outwards. The Irish missionary movement reached its apogee in terms of numbers in the 1920s and 1930s. A very gradual decline until the mid 1960s then accelerated; the movement is no longer the force it was, reflecting the wider drop in vocations.