A few addendums/clarifications to what I wrote earlier:
* Some claim common umlaut use came into being only AFTER the Renaissance period, not earlier.
* Use of Fraktur in Germany was widespread until the 1940s, but also co-existed with Roman type for years before Hitler ultimately opted to unify the country with the across-the-board teaching of the Roman script exclusively. The expense of co-existent character/script teaching throughout the country cannot be discounted in his decision making either.
* My example of G�the may not have been the wisest choice, as I seem to recall seeing this variant the more I think on it. But I do believe there are examples where certain ae, oe, ue combinations are not meant to be rendered with an umlaut.
For all it's worth,
Jb