確信した

was convinced

→ 確信
phrase Common #2,886
was convinced Past form of 確信する, meaning to be certain or convinced that something is true.
JA: 彼は計画が成功すると確信した。
EN: He was convinced the plan would succeed.

彼女の微笑みで、彼は彼女が幸せであると確信した。

Her smile convinced him that she was happy.

あの日僕は確信したギータとバビータはさておき

That day, I became certain—Geeta and Babita notwithstanding.

— ダンガル きっと、つよくなる (2016)

私の考えを説明すると、彼はそれが答えだとすっかり確信した。

When I explained my reasoning, he became completely convinced that it was the answer.

その男は嘘をついているのだと彼女は確信した。

She was convinced that the man was lying.

私は彼が有罪だと確信した。

I was convinced that he was guilty.

私はそれを確信した。

I was convinced of it.

彼女の微笑みで私は彼女の私への信頼を確信した。

Her smile assured me that she trusted me.

私は以前に彼女と会った事が無い事を確信した。

I was certain that I had never met her before.