Which event did Kent State students protest in 1970?

Kent State students protested the expansion of the Vietnam War into Cambodia in 1970. The protest followed President Nixon’s announcement of U.S. military operations there, and the National Guard killed four students during the demonstrations. The Christmas bombing campaign happened in 1972, while the My Lai Massacre and Vietnamization were not the event that prompted the Kent State protest.

AI-written and checked against the verified answer.