I have checked with both a native speaker, and my husband who speaks fluent German and has an MA in German Literature - not that that has anything to do with it!) [Not meaning to offend anyone]
This inscription is almost an invocation it seems.It is difficult to translate literally into familiar English grammar structure, but is on the gist of: With God, my Prince (leader over the region he came from), the Fatherland (I think that it would be used in the context of (eg.) 'I do what I do for/with their blessing.....'.This shows the order of allegiance.Note that the local Prince is higher than the Fatherland; an important aspect of the German worldview.
I surely hope this makes sense.I definitely know that Fuerst in this use is not the name of the individual soldier.