Breakdown of minna wa heiwa ni tsuite hanashimashita.
Questions & Answers about minna wa heiwa ni tsuite hanashimashita.
は marks みんな as the topic of the sentence.
So みんなは means something like as for everyone or everyone, ....
In this sentence, the speaker is telling us what everyone did:
- みんなは = as for everyone
- 平和について話しました = talked about peace
A learner might expect が, but は is very common when introducing what the sentence is about. が would sound more like you are specifically identifying everyone as the ones who talked, often in contrast with someone else.
みんな usually means everyone or everybody.
Even though it refers to multiple people, Japanese nouns do not have to show singular/plural the way English does. So みんな already naturally gives the idea of a group.
Depending on context, みんな can mean:
- everyone
- all of us
- you all
- all of them
In this sentence, it most naturally means everyone.
