Мы отправили документ министру.

Because министру is in the dative case. In this sentence, the minister is the recipient of the document, so Russian uses the dative, like English to the minister.

• Dictionary form: министр
• Dative singular: министру

So:

• Мы отправили документ министру. = We sent the document to the minister.

Документ is the direct object of the verb, so it is in the accusative case. But for many inanimate masculine singular nouns, the accusative looks exactly the same as the nominative.

So:

• nominative: документ
• accusative: документ

That is why you do not see a different ending here.

Отправили is the past tense plural form of отправить. It tells us two important things:

1. The action happened in the past
2. The subject is we (or another plural subject)

It also comes from a perfective verb, so it usually means the action was viewed as completed: the document was actually sent.

Compare:

• отправили = sent, finished sending
• отправляли = were sending / sent (with focus on process, repetition, or background context)

Yes, Russian often omits subject pronouns when they are clear from the verb form.

Because отправили already shows plural past, the sentence could also be:

• Отправили документ министру.

That can still mean We sent the document to the minister, depending on context.
However, мы is included if the speaker wants to:

• make the subject explicit
• create contrast, as in We sent it, not they
• sound a bit clearer

Yes. Russian word order is more flexible than English because the case endings show each word’s role.

The neutral order here is:

• Мы отправили документ министру.

But you could also say:

• Мы министру отправили документ.
• Документ мы отправили министру.
• Министру мы отправили документ.

These all keep roughly the same basic meaning, but the focus changes:

• putting документ earlier can emphasize the document
• putting министру earlier can emphasize the recipient

So word order in Russian often helps show what is new, important, or contrasted.

Russian has no articles like English a/an and the.

So документ can mean:

• a document
• the document

And министру can mean:

• to a minister
• to the minister

The exact meaning depends on context, not on a separate article word.

In this sentence, министру most naturally means to the minister because it is the recipient of отправили.

The dative case often marks:

• the receiver of something
• the person something is given, sent, shown, or said to

So here the relationship is:

• документ = the thing sent
• министру = the person it was sent to

Because Russian past tense agrees with the subject in gender/number, not person the way English present tense does.

For past tense:

• отправил = he sent
• отправила = she sent
• отправило = it sent
• отправили = they sent / you sent (plural/formal) / we sent

Since мы means we, the verb must be plural, so we get отправили.

Here are the dictionary forms:

• мы → мы
• отправили → отправить
• документ → документ
• министру → министр

This is useful because Russian words often change form depending on their grammatical role, but dictionaries usually list the base form.