Meanwhile, the Gulf states believed Iran was backing the Houthis, and feared what America’s support for the nuclear deal meant for them. “The Saudi government was very nervous about the deal, and so the implicit policy imperative of the day was to reassure them,” Rose Jackson, who served as chief of staff at the State Department’s Bureau of Democracy, Human Rights, and Labor from 2013 to 2016, told me. “Simultaneously, they had launched this deeply problematic air campaign, civilians were dying, and a humanitarian crisis was brewing.”

“Larry was initially sent to advise the Saudi government in a good-faith effort to figure out how serious they were about improving their processes and protecting civilians,” Jackson said. “We weren’t sending just anyone. We were sending the guy who had helped our own government establish a system for limiting civilian harm in Afghanistan, with prior military experience, under the auspices of the bureau focused on human-rights and civilian-protection issues … But broadly speaking, if we tried this arrangement out as a test, it failed.”

By the time Lewis settled into his job at the State Department in August 2015, coalition pilots had already hit a staggering number of civilian targets in Yemen, including markets, gas stations, a teachers’ union meeting, and various residential areas. By the end of the month, the United Nations, drawing on cases it could reasonably verify, conservatively reported more than 2,100 civilian deaths in Yemen since March—the majority resulting from coalition strikes. At least some of the civilian deaths likely stemmed from the coalition’s inexperience in waging such a massive air war—the U.S.-led anti-ISIS air campaign has itself killed thousands. There was also a sense that the coalition members didn’t seem to care very much about protecting civilians. Washington’s “targeting assistance” didn’t seem to be doing much to help reduce civilian harm.