As President Trump faced an impeachment trial that raised the possibility Bolton might provide testimony, the White House on January 23 issued a formal threat to stop Bolton from publishing his book, citing national security concerns.[19] Bolton had submitted his manuscript to the National Security Council for security review in December 2019, and after months of discussions, was told on April 27 by Ellen Knight — the NSC's senior director for prepublication review — that no other classification issues remained.