The past five decades have witnessed often fierce international rivalry in space, but also surprising military restraint. Now, with an increasing number of countries capable of harming U.S. space assets, experts and officials have renewed a long-standing debate over the best route to space security. Some argue that space defenses will be needed to protect critical military and civilian satellites. Others argue that space should be a "sanctuary" from deployed weapons and military conflict, particularly given the worsening threat posed by orbital space debris. Moltz puts this debate into...