This is the 9915th most frequent Korean word.
공군기지를
"Air Force base."
In this sentence, '공군기지를' is used as the object of the verb '방문했어요', indicating the noun being acted upon.
나는 공군기지를 방문했어요.
I visited the air force base.
Here, '공군기지를' is part of the object of '건설하기로 했어요', specifying the entity that the action of construction will affect.
정부는 새로운 공군기지를 건설하기로 했어요.
The government decided to construct a new air force base.
In this sentence, '공군기지를' serves as the object of '찾을 수 없었어요', denoting the entity being searched for.