honbu ni renrakusita.

It is read ほんぶ に れんらくした.

• 本部 = ほんぶ
• に = に
• 連絡した = れんらくした

The dictionary form of the verb part is 連絡する (れんらくする).

本部 means headquarters, main office, or head office.

It is a noun. Depending on context, it could refer to:

• a company’s head office
• a police or emergency command center
• the main branch of an organization

So the exact English translation can vary a little depending on the situation.

Here, に marks the target or recipient of the contact.

With 連絡する, the person or place you contact is often marked by に:

• 会社に連絡する = contact the company
• 先生に連絡する = contact the teacher
• 本部に連絡した = contacted headquarters

So に works a bit like to in English, even though natural English usually says contact headquarters rather than contact to headquarters.

連絡する is a very common suru-verb. That means 連絡 behaves like a verbal noun, and adding する makes it into a verb: to contact / to get in touch / to inform.

So:

• 連絡する = to contact
• 連絡した = contacted

You can also say 連絡をした, but it is often less direct and sometimes sounds a little more explanatory or formal depending on context. In many everyday sentences, 連絡した is the more natural choice.

連絡した is the plain past form of 連絡する.

So it tells you that the action already happened:

• 連絡する = contact / will contact
• 連絡した = contacted

It is not specifically marked for he/she/I. Japanese verbs do not change based on the subject the way English verbs sometimes do.

Japanese often leaves out the subject when it is clear from context or not important.

So 本部に連絡した。 could mean:

• I contacted headquarters.
• He contacted headquarters.
• She contacted headquarters.
• We contacted headquarters.

The listener is expected to understand who did it from the situation. This is very normal in Japanese.

This is plain/casual style because it ends in した, not しました.

Compare:

• 本部に連絡した。 = casual/plain
• 本部に連絡しました。 = polite

The plain form is common in:

• casual conversation
• narration
• diary style
• internal thoughts
• informal reports depending on context

It is not rude by itself; it just has a less polite style than しました.

Sometimes yes, but に is more natural with 連絡する.

• 本部に連絡した = the standard, natural way to say contacted headquarters
• 本部へ連絡した = possible, with a slightly stronger sense of direction toward headquarters

In many cases, learners should treat 連絡する as commonly taking に for the person or organization contacted.

The structure is:

本部 + に + 連絡した
headquarters + to/recipient marker + contacted

So the grammar pattern is basically:

[person/place contacted] に 連絡する

Examples:

• 友だちに連絡する = contact a friend
• 病院に連絡する = contact the hospital
• 本部に連絡した = contacted headquarters

Usually it is close, but it can cover a few related ideas depending on context:

• contact
• get in touch with
• inform
• let someone know

For example, 本部に連絡した could mean:

• someone called headquarters
• someone messaged headquarters
• someone reported the situation to headquarters

Japanese does not always specify the communication method unless needed.

Yes. Depending on context, natural translations could include:

• I contacted headquarters.
• We got in touch with headquarters.
• He informed headquarters.
• She called the main office.

Even though the Japanese sentence is short, English often needs you to choose a subject and sometimes a more specific verb based on the situation.