人を守りながら **では** 刀も思い切り振れない does this imply some condition like as in "in the
condition of while protecting people i cant swing the katana as much as i
would like to" this is really bad and unnatural translation, but does it
convey something like this?
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2023-01-04T20:27:42.907
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grammar particle-で
the usage of で in: 人を守りながらでは刀も思い切り振れない
Your interpretation is correct.

A monolingual dictionary has the following entry for
[ては](https://dictionary.goo.ne.jp/word/%E3%81%A6%E3%81%AF/#jn-152199).

> ４
> その条件のもとでは必ず、または常に同じ結果になる場合の、その条件を示す。「慢心してい―勝てない」「せい―事を仕損じる」「遊んではよい成果が得られない」
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2023-01-04T21:19:05.903
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This ～では is like "if it's ～"; this で is not a case particle marking
location/condition, but the te-form of the copula だ. This type of では is
interchangeable with だと.

  * 彼女では無理だ。  
= 彼女だと無理だ。  
If it's her (who tries it), it's impossible.

  * この本では簡単すぎる。  
= この本だと簡単すぎる。  
If it's this book (that I have to use), it's too elementary (and I cannot get
enough information).

You can use the same では after a particle (remember particles work [somewhat
like a no-adjective](https://japanese.stackexchange.com/q/33605/5010) in
Japanese):

  * ここからでは見えない。  
= ここからだと見えない。  
(If it's seen) from here, it's invisible.

  * 彼とでは失敗しそうだ。  
= 彼とだと失敗しそうだ。  
(If it's done) with him, I'll probably fail.

  * 1人ででは難しい。  
= 1人でだと難しい。  
(If it's done) alone, it's difficult.  
(でで is not a typo)

  * 人を守りながらでは刀も思い切り振れない。  
= 人を守りながらだと刀も思い切り振れない。  
I can't even swing a sword casually (if it's done) while protecting someone.

As you can see, this type of では is usually used with an expression claiming
something is inappropriate or impossible. なら or だったら is used if the following
part is affirmative (e.g., あなたと2人でなら問題ない "It's okay if I do it together with
you", 教科書を見ながらだったらできます "I can do it if I do it while seeing a textbook").
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