Learn Hardcore Croatian: Bez putovnice ne možemo preko granice. - Without a passport we cannot cross the border.

In Croatian, bez always takes the genitive case. That is why both putovnice (from putovnica, passport) and granice (from granica, border) are in the genitive singular here.

nominative: putovnica, granica (dictionary form)
genitive: putovnice, granice (used after bez, preko, etc.)

Other examples with bez + genitive:

Bez novca ne mogu. – Without money I cannot.
Bez kišobrana si mokar. – Without an umbrella you are wet.

Why is it putovnice and not putovnica?

Putovnica is the nominative singular (the base form you see in dictionaries).

After bez, you must use the genitive singular, which for feminine nouns ending in -a is usually formed by replacing -a with -e:

nominative: putovnica – passport (subject form)
genitive: putovnice – of a passport / without a passport

So Bez putovnice literally means Without (a/the) passport.

What exactly does ne možemo mean?

Ne možemo is we cannot / we can’t.

infinitive: moći – to be able (can)
1st person plural present: možemo – we can
with ne (negative particle): ne možemo – we cannot

So the core of the sentence is ne možemo = we can’t / we are not able to.

Why is there no verb like “go” or “cross” after ne možemo?

In English we must say we can’t cross / go across the border.

In Croatian it is quite natural to leave the main verb understood if context makes it clear:

Bez putovnice ne možemo preko granice.
= Without a passport, we can’t (go) across the border.

You could also say it with an explicit verb:

Bez putovnice ne možemo prijeći granicu. – Without a passport, we cannot cross the border.

Both are correct; the version in your sentence is just a bit more compact and idiomatic.

What does preko granice literally mean?

Preko means over / across / via, and it also takes the genitive case.

preko granice = across the border / over the border

So the whole sentence is literally:

Bez putovnice – Without a passport
ne možemo – we cannot
preko granice – across the border

Together: Without a passport, we cannot across-the-border → We can’t cross the border without a passport.

Why is it granice and not granica?

Same reason as with putovnice: granica is the nominative; granice is the genitive singular.

The preposition preko always takes the genitive, so you must say:

preko granice – across the border
not
✗ preko granica (wrong for singular)
✗ preko granicu (accusative, wrong after preko)

Pattern (feminine noun in -a):

nominative: granica – border
genitive: granice – of the border / across the border (preko granice)

Is the word order fixed, or can I move things around?

Word order in Croatian is more flexible than in English. Your sentence:

Bez putovnice ne možemo preko granice.

Possible variants (all grammatical, with slightly different emphasis):

Ne možemo preko granice bez putovnice.
Preko granice ne možemo bez putovnice.
Bez putovnice preko granice ne možemo.

The basic meaning stays the same: without a passport, we can’t cross the border. The original order is neutral and very natural. Other orders can slightly stress different parts (for example, starting with Preko granice emphasizes “as for crossing the border…”).

Could I say Bez putovnice ne možemo prijeći granicu instead? What is the difference?

Yes, that is perfectly correct:

Bez putovnice ne možemo prijeći granicu.
= Without a passport, we cannot cross the border.

Differences:

preko granice – preposition phrase (literally over/across the border)
prijeći granicu – verb prijeći (to cross) + direct object (granicu, accusative)

The original sentence with preko granice is a bit more general and colloquial. The version with prijeći granicu makes the action “to cross” explicit and sounds a touch more formal/precise. Both are common and natural.

What tense and person is možemo? How would I say “we couldn’t” or “we won’t be able to”?

Možemo is present tense, 1st person plural of moći (to be able, can):

ja mogu – I can
ti možeš – you can (sg.)
on/ona/ono može – he/she/it can
mi možemo – we can
vi možete – you can (pl.)
oni/one/ona mogu – they can

Other useful forms with this sentence:

Nismo mogli preko granice bez putovnice. – We couldn’t cross the border without a passport.
Nećemo moći preko granice bez putovnice. – We won’t be able to cross the border without a passport.

Why are there no words like “a” or “the” in putovnice and granice?

Croatian has no articles (no words corresponding directly to English a/an or the).

Nouns like putovnica and granica stand on their own, and definiteness or indefiniteness is understood from context:

Bez putovnice ne možemo preko granice.
can mean:
- without a passport we can’t cross the border
  or
- without the passport we can’t cross the border

The language simply does not mark that difference explicitly with separate words. Context tells you which reading is intended.