Early in April 1970, Robert Morris installed an immense jumble of timbers and concrete blocks on the third floor of the Whitney Museum. At the end of the month, President Nixon announced in a nationwide broadcast that the United States had invaded Cambodia; moreover, he said, resistance to the American presence in Vietnam required him to draft an additional 150,000 soldiers into the armed forces. College students launched protests on campuses across the country. When protesters set fire to the ROTC building at Kent State University in Ohio, the National Guard was called in. On May 4, a detachment of guardsmen fired on a crowd, killing four and wounding nine. Like many others, Morris saw in this murderous incident an allegory of the nation's quickening decline.