Washington (CNN) Damaging portraits of President Donald Trump are drawing new attention to the options available to military commanders who feel they have been given an illegal or seriously ill-advised order by their commander in chief.

A New York Times op-ed penned by a "senior official" and excerpts from a new book by Bob Woodward portray Trump as erratic, impulsive and dangerously incurious on matters of national security. The publications illustrate how some of Trump's top advisers believe the President of the United States is unfit to be the most powerful man in the world and have sought to circumvent or undermine his demands.

Defense Secretary James Mattis is among those top officials, according to confidential background interviews conducted by Woodward, who writes that the defense secretary reportedly made disparaging comments about Trump and military actions he sought to take against Syria and North Korea.

Woodward depicts a furious Trump demanding that his military officials have Syrian President Bashar al-Assad assassinated after his regime was accused of conducting a chemical attack against civilians in April 2017. And after a charged meeting about South Korea, during which Trump wondered why the US backs Seoul, Woodward writes that Mattis says Trump understands issues at the level of an elementary school student.

Mattis has denied those assertions, and the accounts detailed by Woodward's sources, including claims that Mattis has ignored or slow-rolled Trump's ideas, seem to fall short of challenging a direct order.

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