On this day, 55 years ago, on May 4, 1970 (March 29, 1970, the lunar calendar), more than 3,000 college students in the United States demonstrated to protest against the U.S. military's invasion of Cambodia and Cambodia. On May 4, 1970, more than 3,000 students from Kent State University in Ohio demonstrated to protest against the U.S. military's invasion of Cambodia. Many students were injured during the police crackdown, and four students were shot and killed, two of whom were female students.