In the post, the president writes that he has approved "a complex operation" to eliminate the Islamist group's second-highest leader, Abu-Bilal al-Minuki.
"As a result, ISIS's global operations have been greatly reduced," Trump writes, thanking the Nigerian government for its cooperation.
"Al-Minuki will no longer terrorize the people of Africa or help plan operations against Americans."
Nigeria has recently suffered several violent attacks claimed by ISIS or its allies. Misdirected attacks by the military have also reportedly killed many civilians.
