Lt. Gen. Jonathan O. Seaman, 74, who commanded the 100,000-man U.S. Field Force II in Vietnam in the mid-1960s and who later commanded the the First Army at Fort Meade, Md., died of cardiac arrest Feb. 18 at the Veterans Administration Hospital in Charleston, S.C.

Gen. Seaman, who retired in 1971 after a 37-year military career, was commander of the 1st Infantry Division ("The Big Red One") at Fort Riley, Kan., when it was ordered to Vietnam in 1965. It became the first Army division to enter combat in the Vietnam War.

In 1966 Gen. Seaman was named commander of U.S. Field Force II, which was made up of three divisions and several independent brigades. In that capacity he planned and directed two major military operations, Junction City and Cedar Falls.

He was commander of the First Army at Fort Meade when he retired and moved to Beaufort, S.C.

Gen. Seaman was born in Manila, the son of an Army officer. He graduated from the U.S. Military Academy at West Point, N.Y. During World War II he served in Europe and the Pacific.

His military decorations included three Distinguished Service Medals, the Legion of Merit, the Distinguished Flying Cross and the Bronze Star.

Survivors include his wife, Mary Grunert Seaman, of Beaufort; two daughters, Wendy Wilson of Alexandria and Penny Linke of Fort Stewart, Ga., and one grandson.