The Year is 1970 ... President Nixon requests a decrease in involvement in Viet Nam called "Vietnamization." U.S. bombing in Vietnam escalates. Protests breakout nationwide after U.S. invades Cambodia. First Earth Day, April 22, for environmental awareness. Four students killed and nine wounded by National Guard during protests at Kent State University. U.S. Supreme Court upholds 18-year-old voting age. U.S. troops in Vietnam down to less than 350,000. Apollo 13 mission is aborted and the lives of astronauts are jeopardized when an oxygen tank explodes in the craft about 200,000 miles from earth on the way to the moon. Clever improvising saves the crew, which returned safely to earth. U.S. population tops 200 million. Chicago Cubs Ernie Banks hits his 500th home run on May 12. Super Bowl IV Kansas City 23, Minnesota 7 Released in 1970. Oscar for special effects. Released in 1970. Oscar for Best Picture and other awards.