A few years ago, with little fanfare, the United States opened a base in the horn of Africa to kill or capture Al Qaeda fighters. By 2012, the Pentagon will have two dozen such forts. The story of Africa Command, the American military's new frontier outpost. The word came down suddenly in early January to the fifty or so U.S. troops stationed inside Camp Simba, a Kenyan naval base located on that country's sandy coast: Drop everything and pull everyone back inside the compound wire. Then they were instructed to immediately clear a couple acres of dense forest. Task Force...