当時は

at that time

→ 当時
phrase Uncommon #14,650
at that time Refers to a particular period in the past; は marks it as the topic. Often translates naturally as “back then.”
JA: 当時は、まだスマートフォンがありませんでした。
EN: Back then, there were no smartphones yet.

当時はホームレスだったんだ

Back then, I was homeless.

当時は旅行よりもずっと大変だった

Traveling was much more difficult back then than it is now.

だが当時はこの言葉は無かった

But at the time, this term didn't exist:

— 帰ってきたヒトラー (2015)

当時はきれいな水がこの川に流れていた

Back then, clean water flowed through this river too.

そしてそのことを当時は警察に言ったんですね

And you told the police about that at the time, right?

— ミスティック・リバー (2003)

当時はトムボストンにいました

At the time, Tom was in Boston.

当時は外国へ行ってしまっていたのを知らなかったのですか

Didn't you know that they had gone abroad by then?

私たちは当時は同級生だった

We were classmates back then.

当時はリッチだったよ

I was rich back then.

当時は日本には鉄道なかった

At that time, Japan had no railways.

あの当時は毎日本当に楽しかったわね

Back then, every day was truly enjoyable.

— 花様年華 (2000)

当時は収入少なく自分の収入だけでは生活できなかった

At the time, my income was low, and I couldn't support myself on it alone.