This might help with the geography -
Bavaria: https://upload.wikimedia.org/wikipedia/commons/5/50/Map-DR-Bavaria.svg
Unified Reich: https://qph.fs.quoracdn.net/main-qimg-d8ec0b8c8f8f0693f576480a64a0235c.webp
German unification was still relatively new by the start of the war. The new Germany was majority Prussian and led by a Prussian Kaiser. The Kaiser had to ask the Bavarians to join him after declaring war even though his declaration was on behalf of all Germany. Each Kingdom had their own War Ministry. Bavaria fought against Prussia as recently as the 1866 Austro-Prussian War, in which they were on the losing side. Regionalism among Germans was still prevalent then. It still is today.
