Stricter Trump administration immigration policies have stymied Pentagon plans to restart a program that allowed thousands of people with critical medical or Asian and African language skills to join the military and become American citizens, according to several U.S. officials. The decade-old program has been on hold since 2016 amid concerns that immigrant recruits were not being screened well enough, and security threats were slipping through the system. Defense officials shored up the vetting process, and planned to relaunch the program earlier this month. But there was an unexpected barrier when Homeland Security officials said they would not be able...