The Senate has begun debate on legislation that could force a broad review and restructuring of the Pentagon's top acquisition programs as the U.S. military wrestles with plans to prioritize global competitions with China and Russia over counterterrorism missions in the Middle East. A provision in the Senate Armed Services Committee's fiscal year 2019 defense authorization bill orders the Pentagon to conduct a "roles and missions" review that includes a "revalidation" of the requirements for multibillion-dollar programs like the Joint...