technically or legally, did I take an oath to abandon my allegiance to my former country?

[cafeconleche]

Can't you go back to Germany and get your passport renewed there?

 

[MartinAub]

Likely, but that would be cheating and I am sure they find that out sooner or later.
Also, you can't just do that on a visit since you need to be registered there as a resident.

 

[Triple Citizen]

One more condition. The US citizen also intends to renounce his/her US citizenship. The State Department assumes that is not the case by default.

I remember reading somewhere on the US Govt Travel site that once you are a US citizen AND you voluntarily accept the citizenship of another country, then you have automatically surrendered your US citizenship.