Why did President Reagan send Rumsfeld to Iraq as noted in the nonfiction book, The Afghanistan Papers?

Rumsfeld was sent by President Reagan as an envoy to Iraq during the Iran-Iraq War that lasted from 1980 to 1988. This accounts for the 1983 image of Rumsfeld shaking hands with Saddam Hussein that would decades later become infamous as a symbol of the Secretary of Defense’s duplicity. As Middle East envoy, Rumsfeld helped convey material US support for Iraq in its war with Iran.