WASHINGTON — President Eisenhower overruled some of his military commanders in the summer of 1958, ordering them not to use nuclear weapons against China if communist forces blockaded the Taiwan Strait, according to declassified Air Force documents.

Eisenhower “made it clear that the Chinese would be given a warning with conventional explosives before he would authorize dropping of the deadlier ordnance” on Chinese territories, according to the documents made public by George Washington University’s National Security Archive.

The president had the support of a congressional resolution to use force in defense of Taiwan. His decision not to use nuclear weapons still left them available if needed for subsequent attacks, according to the newly released narrative by a contemporary Air Force historian, Bernard C. Nalty.

Disclosure of the top-secret document was one in a collection obtained by a freedom-of-information lawsuit filed by the archive after more than a decade of requests that the documents be declassified, William Burr of the archive said.

As the crisis grew, according to the papers, five B-47 bombers on Guam went on alert in mid-August to conduct nuclear raids against Chinese airfields.

The idea of using nuclear weapons to prevent the Chinese from using ships and aircraft to isolate Nationalist-held islands in the strait was accepted by Eisenhower’s Cabinet — except for Secretary of State John Foster Dulles, who was away on vacation. But Eisenhower ruled out the initial use of nuclear weapons, concluding the fallout would cause civilian casualties in China and on Taiwan, risking nuclear escalation.