Final answer:
President Reagan asked Congress to authorize $20 billion for the purpose of strengthening national defense through the Strategic Defense Initiative (SDI), also known as 'Star Wars.'
Step-by-step explanation:
President Reagan asked Congress to authorize $20 billion for the purpose of strengthening national defense. As part of Reagan's plan to increase defense spending, he led an unprecedented military buildup, which included funding for expensive new forms of weaponry.
The $20 billion was intended to support the Strategic Defense Initiative (SDI), also known as 'Star Wars,' which aimed to develop a defensive shield to protect the United States from a Soviet missile strike.