Rabb Professor of Government Joseph S. Nye Jr. is expected to resign from Harvard and remain indefinitely in Washington, D.C., pending Senate confirmation as the new assistant secretary of defense for international security affairs.

Nye is an immensely popular professor who is best known for teaching the core course "Historical Studies A-12: International Conflict in the Modern World." He was described in the 1993 Confidential Guide to courses as "godfather and possessor of the most dedicated cult of personality since Mao."

Nye was expected to return from Washington by February 1, 1995, when his leave of absence expires. But if confirmed by the Senate this week, Nye indicated yesterday that he will immediately assume his new duties, setting policy on all regional security issues.

That means the professor, once a serious contender for both Harvard's presidency and the deanship of the Faculty of Arts and Sciences, will be forced to give up his Harvard tenure and formally resign. Tenured professors cannot be off campus doing non-University work for more than two years.

Nye began his two-year leave of absence in early 1993 after President Clinton appointed him to his current post: chair of the CIA's National Intelligence Council.

Between 1977 and 1979, Nye served as deputy under-secretary of state under President Jimmy Carter and chaired the National Security Council group on non-proliferation of nuclear weapons.

If confirmed, Nye will head the Defense Department's "little State Department," taking responsibility for defense dealings with all other areas of the world, including Bosnia, Somalia, Haiti and North Korea.

"Of course one hesitates to give up a position on the faculty at Harvard because that is a fascinating job," Nye said.

"But government work is also fascinating, especially given the uncertainties we face today and the immediacy of the problems I've been dealing with," he said. "It's hard to break that off, but at the same time, leaving Harvard is not something that's done lightly."

The Senate Armed Services Committee endorsed Nye's nomination last month. His full Senate confirmation hearings this week, however, is "just a necessary formality at this point," said Commander Chuck Franklin, Department of Defense spokesperson.

Reischauer Professor of Japanese Politics Susan J. Pharr, chair of the Government Department, said Monday that the department had planned for his departure when they scheduled this year's course offerings.

Nye said initially that he would resume teaching A-12 this spring.

Instead, Nye will be replaced for the second year in a row, this time by Associate Professor of Government Stephen Peter Rosen and Assistant Professor of Government Andrew Moravcsik.

When Nye last led the course in the fall of 1992, he received an unusually high CUE guide rating of 4.7 out of 5, and enrollment peaked at 595.

But the number of students dropped to 202 last year when Dillon Professor of the Civilization of France Stanley Hoffmann and Assistant Professor of Government J. Lawrence Broz co-taught the course.

Students who had waited for Nye's return to take A-12 said yesterday that they are part disappointed, part peeved.

"I totally can't believe it. I feel like I've been screwed," said one junior government concentrator who passed up Hoffmann and Broz, hoping to absorb Nye's first-hand knowledge of foreign policy this year.

Another concentrator, Joel J. Radtke '96, said last spring that Nye gave inspiring lectures that were "actually, unbelievably, fun."

"I feel really lucky to have taken A-12 when I did," Radtke said. "His absence really put a crimp in some people's curriculum."

But Nye said his absence allows A-12 students to have the best of both worlds. Now they can read Nye's book, Understanding International Conflict, based on his A-12 lectures, while being taught in class by another professor.

"They get two for one while I'm gone," he said. "They can have all my ideas at home and someone's else's ideas in the classroom. It's a great situation for A-12 students."

Last March, Nye also said he would teach courses on American foreign policy and ethics and international politics, as well as a government department junior seminar, when he returned.

Despite his resignation, Nye said he plans to re-join Harvard's faculty in a few years, "if they'll have me."

"And if I do return, I'll have a deeper knowledge of what it's like to make policy. That will eventually translate into my teaching and writing," Nye said.

Nye can apply for re-appointment at anytime. And if Pharr has her way, the intelligence expert will be back soon.

"It's certainly never automatic that a professor who has relinquished tenure will be invited to return, but considering what a superb, outstanding scholar Professor Nye is, I personally would strongly support him," Pharr said.

"We'll go on without him, but Professor Nye's departure is a significant loss to our department," she added.

Dean of the Faculty Jeremy R. Knowles said he remains committed to Harvard's tradition of supporting its faculty if they choose to pursue public service. But he lamented the loss of Nye.

"I am delighted for the country, I am pleased for Professor Nye," he said last night, "but I am miserable for Harvard.