From Church and State, UK
In the 1500s the Vatican aligned itself with its favorite despots — and the Protestants cuddled up to their preferred tyrants. Each religion claiming divine sponsorship — each ruler laying claim to whatever land the ruler next door happened to occupy. After the Diet of Speyer, the principle of cuius region, eius religio (The religion of the ruler is the religion of the ruled) was established and this really clarified matters for all concerned — at least it did if you were a ruler. As battles raged, frontiers shifted backwards and forwards, countries were claimed and conquered depending on who was victorious. Armies advanced and retreated and a peasant could find himself being a Protestant at breakfast time and a Catholic by lunchtime (if you were a Jew you would be dead by teatime).
With the capture of land came the capture of souls. The religion of the victorious army was imposed on the conquered: it happened with almost all religions all over the world.
In Saudi Arabia during the 18th century a man called Ibn Al-Wahhab, an extreme Islamic fundamentalist who believed that music and reproductions of the human image should be banned and that all non-believers should be beheaded, cozied up to Mohamed Ibn Saud, founder of Saudi Arabia, promising him that the Wahabi movement would help him achieve “power and glory” and gain him conquest over “the lands of men.” And conquer, he did.
But let’s deconstruct such a scenario.
Any invading army with colonial aspirations first gains control of the resources and geography of their “enemy.” They then forcefully impose the religious and political ideology on the extant population of adults. But what about the children? If a religion is not to die with the first generation upon which it has been imposed, then that religion must be propagated through the generation which will succeed them. Children must therefore become indoctrinated, and such indoctrination comes at the hands of their parents and whatever teacher/priest/imam happens to have access to them.