President Bush can safely claim a positive legacy in Africa, which he tours starting Feb. 15. He increased funds for health and tied foreign aid to reform. But one legacy hangs in the balance: a new American security arrangement there. It's called AFRICOM, a United States military command center for the continent. It replaces a cold-war setup that viewed Africa as secondary to larger security concerns. That's why its oversight was long divided among three US command centers that focus on other global regions.