The Pentagon's No. 2 uniformed military officer has launched a campaign to identify the "most pressing military needs" of U.S. forces, an effort that is expected to produce a short list of new, high-priority weapon system requirements and set in motion an unprecedented top-down process for determining what combat capabilities the Defense Department buys. Adm. Edmund Giambastiani, vice chairman of the Joint Chiefs of Staff, is distilling the list of new requirements along with the service vice chiefs of staff,...