Troppene befrir byen.

Because troppene is the definite plural form of the noun.

The pattern is:

• en tropp = a troop / a unit
• troppen = the troop
• tropper = troops
• troppene = the troops

So the ending -ene here works like English the + plural.

In Norwegian, the definite article is usually attached to the end of the noun rather than written as a separate word.

So:

• by = city / town
• byen = the city

and

• tropper = troops
• troppene = the troops

That is a very common feature of Norwegian nouns.

Because by is a common-gender noun in Bokmål.

Its forms are:

• en by = a city / town
• byen = the city / town

If it were a neuter noun, you would expect et in the indefinite form and often -et in the definite singular. But by is not neuter; it is common gender.

Befrir is the present tense of å befri.

So:

• å befri = to liberate
• befrir = liberates / is liberating

Many Norwegian verbs form the present tense with -r. Since the infinitive here is befri, the present tense is befrir.

It can mean either, depending on context.

Norwegian often uses the simple present where English might use either:

• liberates
• is liberating

So Troppene befrir byen can describe a general present statement or an action happening now. Context tells you which English translation sounds best.

It is the normal subject–verb–object order:

• Troppene = subject
• befrir = verb
• byen = object

So the structure is:

The troops + liberate / are liberating + the city

This is the most neutral word order for a simple Norwegian main clause.

Mostly from word order and meaning.

In a neutral Norwegian statement, the subject usually comes before the verb:

• Troppene befrir byen = The troops liberate the city

If you reverse the nouns, you change the meaning:

• Byen befrir troppene = The city liberates the troops

Norwegian nouns do not usually change form for subject vs. object the way some other languages do, so position is very important.

No. This is a false friend.

In Norwegian, by means city or town.

It is not related in meaning to the English preposition by.

So byen means the city / the town, not anything like English by.

Yes. Norwegian by can cover both town and city, depending on context.

So byen may sometimes be translated as:

• the city
• the town

If your learning material gives city here, that is a perfectly normal translation.

A rough pronunciation guide is:

• Troppene ≈ TROP-eh-neh
• befrir ≈ beh-FREER
• byen ≈ BEE-uhn, but with the Norwegian y sound, which is not the same as English ee

A more helpful note for English speakers is:

• troppene has the stress at the beginning
• befrir has the stress on the second part: -frir
• byen contains the Norwegian vowel y, which is rounded and may take practice

So the whole sentence is approximately:

TROP-eh-neh beh-FREER BEE-uhn

but with a Norwegian-style y sound in byen.