caleb melby with bloomberg news, renato mariotti, thank you both. >> woodruff: as the ongoing civil war in yemen is leaving more and more civilians dead, nick schifrin looks at the ited states' role in the conflict. >> schifrin: since early 2015, a saudi-led coalition has been fighting iranian-aligned houthi rebels in yemen. yesterday, the houthis and the u.n. blamed the coalition foan attack in yemen's west that reportedly killed 30 people, including women, andany children. the coalition disputes that claim.r earlis month, the u.n. says a coalition airstrike hit a school bus, killing east 51 people, including 40 children.s the u.s. provipport to the coalition, and now congress is calling for the pentagon and white house to better describe that support. some on capitol hill want the u.s. to cease its involvement all together. for more on this, we are joined from irut by kristine beckerle, the yemen researcher at human rights watch, and the lead author of a report released today, "hiding behn:d the coalitailure to credibly investigate and provide redress fo"unlawful attacks in yeme krist