Who wrote the poem with lines Rest easy sleep well your brothers?

The poem you are referring to is "The Ballad of the Green Berets" written by Robin Moore.

The lines you quoted are:

> Rest easy, sleep well, your brothers are here.

> We'll carry on the fight, with honor and fear.

This poem, often considered the anthem of the U.S. Army Special Forces, was first published in 1965 and gained immense popularity during the Vietnam War. It was later set to music and became a popular song, further amplifying its reach and impact.