Since Russia invaded Ukraine on February 24, the U.S. has significantly escalated its support for Kyiv, both militarily and rhetorically, reflecting a growing mission creep that comes with the risk of provoking Moscow. Early on in the invasion, the U.S. was wary of confirming details of military aid, intelligence sharing, and training of Ukrainian forces. But now, U.S. officials are speaking openly about how Washington is helping Ukraine in its fight against Russia. Last week, anonymous U.S. officials speaking to the media claimed U.S. intelligence had helped Ukrainian forces kill Russian...