A former top military commander says the advent of cyber weapons could give U.S. officials much-needed options for neutralizing enemy missiles short of shooting them down mid-flight. Unleashing virtual attacks against missile-relevant targets would be preferable to attacks with conventional weapons, retired Marine Corps Gen. James Cartwright argued, as defense leaders debate game-changing approaches to a problem that they say is becoming unmanageable with traditional missile-defense doctrine. Cartwright, a former vice chairman of the joint chiefs of staff, said it...