Learn Croatian: Zapovjedniče, neprijatelj je ispred zida! - Commander, the enemy is in front of the wall!

Zapovjednik is in the Vocative case because the speaker is addressing the commander directly. For masculine nouns ending in -k, the -k changes to -č before the Vocative ending -e. This sound change is called palatalization, which is exactly what you are practicing in this lesson!

Why is the word for wall zida instead of zid?

The preposition ispred (in front of) always requires the noun that follows it to take the Genitive case. Since zid is a regular masculine noun ending in a consonant, it adds the -a ending to become zida.

Could we say 'Neprijatelj ispred zida je!' instead?

No, because je is an enclitic (an unstressed word) that strongly prefers the second position in its clause. After the comma, neprijatelj acts as the first position of the main clause, so je must immediately follow it.

Is the word neprijatelj literally made up of the words for not and friend?

Yes! It is formed by attaching the negative prefix ne- (not) to prijatelj (friend). While it literally translates as non-friend, it is the standard Croatian word for an enemy.