lat6

Nominative    - corpus

Genitive        - corporis

Dative           - corporI

Accusative     - corpus

Ablative        - corpore

Nominative     - corpora

Genitive         - corporum

Dative           - corporibus

Accusative     - corpora

Ablative        - corporibus

1. "We" are the unexpressed subjects.

2.  corpora is nominative because the bodies are identified with the subject. Not a direct object.

3. statements of identity using the  nominative case  are "predicate nominatives."

HostEs - masculine nominative noun, enemy,  The context makes it clear that it is the subject of pugnant, rather than accusative. 

ex - preposition related to ablative case, meaning "out of", "from" or "from on top of"

Pugnant - indicative, "they fight"