The U.S. Air Force must modernize its aging arsenal of B-61 and B-83 thermonuclear freefall bombs if the nation is to maintain its deterrence, especially against emerging atomic powers, service officials said. But the weapons are funded partly by the Department of Energy and partly by the Pentagon, which has complicated modernization efforts. Testifying before the House Armed Services Committee on Nov. 2, Air Force Chief of Staff Gen. Norton Schwartz made an appeal for that panel to ask the Department of Energy to modernize the B-61 bomb, which makes up the preponderance of the U.S. aircraft-dropped tactical nuclear arsenal.