..Charlemagne gave orders that every Saxon who chose to remain
unbaptized was to be put to death...
sometimes whole tribes were made to pass through a shallow stream
and amid the splashing a cleric would pronounce the 'words of
baptism'.
..at least one cleric kept his sanity in the midst of absurdity
and said (..) You may indeed force him into being baptized but
not into believing.

The reader will probably see forced baptism as a piece of
devilish mockery - and it is. But...
when Church and State are considered one, then forced baptism
is altogether reasonable.
The state can tolerate no citizen who refuses to be considered
a member of the state, nor will the church establishment tolerate
such a one if it considers itself coextensive with the state.

In "Christendom", good standing in the state requires good
standing in the church and vice versa. Forced baptism is
therefore.. as reasonable as universal military service or
common taxes.
Moreover, .. 'christening' [babydåp] is in itself a kind of
forced baptism, opening the way into forced baptism in the
life of adults. (..)

following Augustine.. the 4th Lateran Council taught that
"they who have once been brought into the faith are not to be
permitted to turn back from it".. it was an official teaching
that when heretics returned from error, their penitence was
to be accepted, "but not to the point of escaping the death
penalty thereby."