The student strike of 1970 was a massive protest across the United States, that included walk-outs from college and high school classrooms initially in response to the United States expansion of the Vietnam War into Cambodia. Nearly 900 campuses nationwide participated. The strike began May 1, but increased significantly after the shooting of students at Kent State University by National Guardsmen on May 4. While many violent incidents occurred during the protests, they were, for the most part, peaceful.