Read the excerpt from Ronald Reagan's "Tear Down This Wall" speech.While we pursue these arms reductions, I pledge to you that we will maintain the capacity to deter Soviet aggression at any level at which it might occur. And in cooperation with many of our allies, the United States is pursuing the Strategic Defense Initiative—research to base deterrence not on the threat of offensive retaliation, but on defenses that truly defend; on systems, in short, that will not target populations, but shield them. By these means we seek to increase the safety of Europe and all the world.