It must have seemed like a problem from hell: When Samantha Power served as Barack Obama’s ambassador to the United Nations, she tirelessly highlighted the depredations of Syrian dictator Bashar al-Assad, publicizing his various barbarities—his indiscriminate killing of civilians, his use of chemical weapons, his astonishing cruelty to children. And yet Ambassador Power served a president who steadfastly refused to do anything to counter those outrages, a president who stood idly by as the Syrian tyrant dropped chemical weapons and barrel bombs on innocent civilians. Indeed, Barack Obama would have fit quite well into A Problem From Hell, Power’s terrific 2003 book, which trained a gimlet eye on America’s all-too-common indifference to genocide and mass killing.

Since her retirement from government service, Power has kept up the fight, tweeting prolifically about the carnage in Syria. Indeed, on April 4, 5, and 6 she tweeted repeatedly about the Assad regime’s apparent chemical assault in Idlib—the very attack that spurred Donald Trump to enforce Barack Obama’s red line and hit back at the Syrian dictator with a missile attack on an air base.