Obama visits Hiroshima to ponder "terrible force unleashed"

By Minami Funakoshi HIROSHIMA, Japan (Reuters) - Barack Obama became the first incumbent U.S. president to visit Hiroshima on Friday, laying a wreath at the site of the world's first atomic bombing in a gesture Tokyo and Washington hope will showcase their alliance and invigorate efforts to end nuclear arms. The two governments hope Obama's tour of Hiroshima, where an atomic bomb killed thousands instantly on Aug. 6, 1945, and some 140,000 by the year's end, underscores a new level of reconcilia