The Defense Department, which two years ago expressed doubts over near-term prospects for fielding an affordable hypersonic strike weapon, has promised U.S. commanders in Europe and the Pacific an initial hypersonic strike capability between fiscal years 2018 and 2022. This change of plans -- revealed in previously unreported written responses from then-Secretary Ash Carter to House lawmakers in 2015 and 2016 -- come as the Pentagon is readying later this year to conduct Flight Experiment 1, a pivotal event in...