だとは知らなかった

I didn't know that…

→ だ
phrase Uncommon #15,767
I didn't know that… Follows a statement to show that the speaker was unaware of it; だ is used after nouns and な-adjectives.
JA: 彼が医者だとは知らなかった。
EN: I didn't know he was a doctor.

トムがダンスの先生だとは知らなかったよ。

I didn't know Tom was a dance teacher.

あなただとは知らなかったよ

I didn't know it was you.

— ウィキッド ふたりの魔女 (2024)

今まで兄弟だとは知らなかった。

I never knew they were siblings.

トムはその赤ん坊がメアリーだとは知らなかった。

Tom didn't know that the baby was Mary.

彼があんなにひどい状況だとは知らなかった

I didn't know he was in such a terrible situation.

— 善き人のためのソナタ (2006)

あっ、ごめん、違法だとは知らなかったよ。

Oh, sorry, I didn't know it was illegal.

私は彼が日本人だとは知らなかった。

I didn't know he was Japanese.