A Warning is a 2019 book about the Trump administration, anonymously authored by someone described as "a senior Trump administration official", revealed in late 2020 to be Department of Homeland Security official Miles Taylor. It is a follow-up to an anonymous op-ed published by The New York Times in September 2018. The article, "I Am Part of the Resistance Inside the Trump Administration", described President Donald Trump's decision-making as uninformed and irresponsible, and said that many current members of the administration deliberately undermine his suggestions and orders for the good of the country.