WASHINGTON — William Knowlton, a retired four-star general who during four decades of military duty was superintendent of the U.S. Military Academy at West Point, died Sunday at Virginia Hospital Center in Arlington, Va., of intracranial bleeding as a result of a fall. He was 88 and had Parkinson’s disease.

Knowlton, a graduate of West Point in January 1943, was the 49th superintendent of the academy, a post he held from 1970 to 1974. At the time, he was the longest-serving superintendent since World War II.

His tenure there reflected the uproar of the culture as the Vietnam War was coming to a close. Knowlton’s attempts to tighten discipline and enforce rules were met with several lawsuits.

He described his job there as “the commander of a stockade surrounded by attacking Indians,” in “The Long Gray Line,” a history of West Point.