Book excerpt: Most people think Star Wars began with the ideas of Ronald Reagan, but its roots reach decades further back. In this first scholarly account of the origins of the Strategic Defense Initiative (SDI), historian Don Baucom traces these roots back to the dawn of the missile age in 1944. He finds SDI emerging after a period of nearly 40 years from forces generated by technological developments, changing strategic conditions, and the collapse of the SALT arms control negotiations of the 1970s.