They rushed to Ukraine by the thousands, many of them Americans who promised to bring military experience, money or supplies to the battleground of a righteous war. Hometown newspapers hailed their commitment, and donors backed them with millions of dollars. With Legion growth stalling, Ryan Routh, a former construction worker from Greensboro, N.C., is seeking recruits from among Afghan soldiers who fled the Taliban. Mr. Routh, who spent several months in Ukraine last year, said he planned to move them, in some cases illegally, from Pakistan and Iran to Ukraine. He said dozens had expressed interest We can probably purchase...