I'm considering applying to master's programs in mathematics over in Germany (e.g. Bonn, Berlin Mathematical School). The stated time for these programs is two years.
Should I get accepted and attend, are there any issues (ethical or otherwise), with bailing after a year to attend a PhD program in the US? If so, is it possible to complete the program in a single year if I come in with some kind of advanced standing (i.e. having taken many graduate courses beforehand)?