This is the 15127th most frequent Russian word.
полковнику
"Полковнику" is the dative case of "полковник," meaning "to the colonel" in English.
In this sentence, "полковнику" is used in the dative case as the indirect object of the verb "сообщили" (informed). It indicates to whom the news was reported.
Полковнику сообщили важные новости.
The colonel was informed of important news.
Here, "полковнику" is in the dative case, reflecting that the colonel is the recipient of the responsibility entrusted by the subject.
Мы доверили полковнику руководство операцией.
We entrusted the colonel with the leadership of the operation.
In this sentence, "полковнику" is again in the dative case, showing that the action of bringing the tea is directed towards the colonel.