Polis eski düşmanı gördü.

Because the most neutral Turkish word order is Subject–Object–Verb.

So:

• Polis = subject
• eski düşmanı = object
• gördü = verb

This verb-final pattern is very common in Turkish. English usually prefers Subject–Verb–Object, so this often feels backwards at first to English speakers.

Other word orders are possible in Turkish, but they usually add emphasis or change the focus.

In this sentence, polis has no case ending, which is normal for a subject in Turkish. The subject is usually in the nominative, and the nominative has zero marking.

Meanwhile, düşmanı has an ending that marks it as the direct object. So the sentence means that the police officer / police did the seeing, not the enemy.

A useful comparison:

• Polis eski düşmanı gördü. = the police officer saw the old enemy
• Eski düşman polisi gördü. = the old enemy saw the police officer

In the second sentence, polisi is marked as the object.

Here, -ı is the accusative suffix, used for a definite or specific direct object.

• düşman = enemy
• düşmanı = the enemy / that enemy, as a direct object

So eski düşmanı means something like the old enemy as the thing being seen.

The vowel is -ı because of vowel harmony. The last vowel in düşman is a, so the accusative becomes -ı.

Turkish does not have articles like English a/an and the.

Instead, Turkish often shows definiteness in other ways:

• through context
• through word order
• through case marking

In this sentence, the object is understood as definite partly because of the accusative ending -ı on düşmanı.

So where English says the old enemy, Turkish can simply say eski düşmanı.

In Turkish, adjectives normally come before the noun they describe, just like in English:

• eski düşman = old enemy

Also, Turkish adjectives do not change for:

• singular/plural
• gender
• case

So eski stays eski in all of these:

• eski düşman = old enemy
• eski düşmanlar = old enemies
• eski düşmanı = the old enemy

That is much simpler than in many European languages.

By form, polis is singular. The regular plural would be polisler.

So grammatically, this sentence most naturally means the police officer saw the old enemy.

However, depending on context, English might sometimes translate polis more loosely as the police. That is a translation choice, not a plural ending in Turkish.

For a beginner, it is safest to learn:

• polis = police officer
• polisler = police officers

gördü breaks down as:

• gör- = see
• -dü = past tense

So it means saw.

The past tense suffix is often taught as -DI, because its vowel and consonant change according to sound rules:

• gör- ends in a voiced sound, so we get d, not t
• the last vowel in gör- is ö, so vowel harmony gives ü

That is why it becomes gör-dü.

Turkish often leaves pronouns out when the subject is already clear.

Here, the subject is explicitly stated as polis, so there is no need to add o.

In fact, adding o would usually sound more emphatic or contrastive rather than necessary.

This is very normal in Turkish:

• Polis gördü. = The police officer saw.
• O gördü. = He/she saw.
• Polis eski düşmanı gördü. = The police officer saw the old enemy.

eski can mean either old or former, depending on context.

For example:

• eski arkadaş = old friend / former friend
• eski müdür = former manager
• eski ev = old house

With düşman, eski düşman can mean:

• an old/longtime enemy
• sometimes a former enemy, depending on context

So the exact nuance comes from the situation, not from the word eski alone.

Yes, as a form on its own, düşmanı can look ambiguous to learners.

It can resemble either:

• düşman + accusative = the enemy
• düşman + 3rd person possessive = his/her enemy

But in this sentence, the intended reading is the accusative object: the old enemy.

If Turkish wanted to say saw his/her old enemy clearly as a definite object, it would usually be:

• eski düşmanını

So this sentence is best understood as the simpler accusative pattern, not a possessive one.