While I'm not an expert myself, I've seen several references stating that being a 100% Jew was no problem at all in German armed forces during WWI. It also seems that during the Nazi years quite a few of these men were for some time "saved" by having been decorated for bravery during WWI.

I've even seen a number of references stating that during WWII there were several partly jewish officers in the KM that were on-purpose left untouched. In fact, none other than Admiral Lütjens's (the one who died on the Bismarck) was 1/4 jewish himself, had a 1/2 jewish wife, and actively protected jews under his command. For instance, his first staff officer on board the Bismarck, Commander Paul Ascher, also was a half-jew.