Croatia is the western edge of a line that runs down through the Balkans and has been drawn and redrawn since the division of the Roman Empire: Latin Christianity on one side, Greek on the other. Croats took their Christianity from Rome and their alphabet, eventually, from the Latin script, while Serbs took theirs from Constantinople and wrote in Cyrillic, and the two peoples speak varieties of one language. That is why religion in this region works as an ethnic marker in a way it does not in countries where language already does the job, and why the wars of the 1990s mapped so exactly onto confessional lines.
There is an older Croatian peculiarity worth recording. The Glagolitic alphabet, the oldest Slavic script, survived in Croatian coastal and island parishes for centuries in Roman Catholic use, with the liturgy celebrated in Church Slavonic under papal tolerance. Priests trained in it were known as glagoljasi, and the Baska tablet from around 1100 is among the earliest monuments of the Croatian language.
The Catholic Church's present legal position rests on four agreements concluded with the Holy See in 1996 and 1998, covering legal status, economic questions, education and culture, and pastoral care in the armed forces and prisons. They provide state funding, tax exemptions and religious instruction in state schools on terms no other religious body in Croatia holds, and they are treaties, so they cannot be altered by ordinary legislation. Attempts to reopen them have not gone far.
Marian devotion is strong. The national shrine at Marija Bistrica draws the largest pilgrimage in the country.