Marius Jansen, a U.S.-trained historian of modern Japan and professor emeritus of Princeton University, died Sunday at a New Jersey hospital, Princeton officials said Tuesday. He was 78.

Although the cause of death was not immediately known, he reportedly had been ill for a long time.

Jansen, a member of the Japan Academy, specialized in researching Japan's transition from the Tokugawa Period (1603-1867) to its rise as a modern state.

Jansen's 1961 study "Sakamoto Ryoma and the Meiji Restoration" has been hailed as a classic in the field by scholars in Japan as well as the West.

His last book, "The Making of Modern Japan," was only published by Harvard University Press about a week before his death.

Jansen last year became the first non-Japanese recipient of the Distinguished Cultural Merit award from the Japanese government.

Born in the Netherlands, Jansen immigrated to the United States and studied Japanese while serving in the U.S. Army during World War II. He graduated in 1944 from Princeton, where he taught for most of his career.

A funeral service will be held Saturday at Nassau Presbyterian Church, in Princeton, N.J.

In lieu of flowers, contributions may be sent to a scholarship fund in the name of Marius B. Jansen at the East Asian Studies program, 211 Jones Hall, Princeton, NJ, 08544-1008.