LONDON — It has been that time of year when Christians, in the West at least, gather to count their blessings. Churches more used to the murmured orisons of shrinking congregations suddenly fill with worshipers singing carols, punctuating less-spiritual rites of frenetic spending that mimic the feast days of the faithful — Black Friday, Cyber Monday.

Only this week, on the 12th day, did the moment come for many to strip the decorative lights from Christmas trees and pack the baubles and tinsel away until next December, making room, perhaps, for darker thoughts.

Rarely, if ever, it seems, has this Western blend of belief and materialism been so remote from the experience of hundreds of thousands of Christians elsewhere struggling to cope with an unwanted and bloody collision with the Islamic exclusivism of jihadists, primarily in Iraq, Syria and Nigeria. And rarely have Western worshipers seemed so reluctant to acknowledge that their faith could be entering the final stage of its long decline in the lands where it was born and first propagated.

For decades, Christian communities in the Holy Land have dwindled, squeezed between the competing claims of Israelis and Palestinians and threatened by Islamic militancy.