Read the sentence. my brother said, “they [the samurai] were the fiercest warriors in the world.” why is the phrase the samurai enclosed in brackets? to show that the enclosed words are foreign to show that the enclosed words are not true to show that the phrase is exclamatory to show that it is not part of the direct quotation

The phrase "the samurai" is enclosed in brackets for the following reason:

To show that it is not part of the direct quotation.

Explanation:

It is a quotation, and as so one cannot alter what was said nor how it was said. However, if some kind of clarification is made necessary, inserting additional words in brackets is the way to go.

As an example, we have magazines in which there are interviews and photographs with captions below them. In order to get someone to be interested in reading that interview, quotations are used with brackets that help the reader identify their context. Eg:

"Protest non violently, because violence begets violence. They  [the establishment] know how to fight violence, because they have been doing it for thousands of years oppressing us and the only thing they don't know about is non violence and humour."

John Lennon during the Bed-In for Peace in Montreal, Canada, in 1969.

you need to make an explanation. so, since you did not include one, so no one, and i mean no one can unfortunately you,