en_tn/isa/59/18.md

He repaid them

Isaiah is describing a future event as if it happened in the past. This means that it will certainly happen.

wrath on his adversaries

The word "wrath" is a metonym for the punishment he brought on his adversaries. Alternate translation: "punished his adversaries for wha they had done" (See: rc://en/ta/man/jit/figs-metonymy)

he repaid recompense to the islands

"he punished the islands as they deserved"

the islands

This phrase is a metonym for the people who lived on the islands or coastlands. Alternate translation: "teh people who live on the islands" or "the people who live on the coastlands" (See: rc://en/ta/man/jit/figs-metonymy)