And so it seems, Robert Gates really will be leaving the Pentagon soon.

He’s been going around to the military academies—West Point last week, the Air Force Academy today, Annapolis sometime soon—bidding farewell to the cadets, pointedly noting at the start of each speech that it will be his “final” address to them as secretary of defense. But Gates is not indulging in valedictory bromides. He’s using the occasions to lay out his vision of what each branch—and each future officer—of the U.S. armed forces must do, and not do, to meet the threats of the 21st century.

He’s given bits and pieces of these speeches before: The Army needs to shift from a garrison peacetime force that’s preparing for a possible head-on armored clash against a foe of comparable strength to a mobile force that’s fighting actual “asymmetric” wars against rogue states and insurgents. The Air Force needs to pull back from its traditional obsession with high-tech air-to-air combat and focus more on joint operations—surveillance, precise air strikes, cargo transport, and rapid rescue—that help the troops on the ground. The Navy needs to focus less on aircraft carriers and more on vessels that can maneuver in coastal waters.

In short, as he put it in these most recent speeches, the “defense bureaucracy,” with its “parochial tendencies” and “institutional constipation,” must abandon its “nostalgia” for Cold War ways and adapt to the modern, messy world. The Pentagon has to learn the lessons of Iraq and Afghanistan, and incorporate those lessons into its culture.

Gates has spent much of these past two years force-feeding these lessons to the Pentagon bureaucracy, and his big worry is that—once he’s gone and, especially, once the current wars wind down and thus the urgency dissipates—things will revert to form. The bureaucrats will heave a sigh of relief and go back to doing what they’ve long thought a “normal” Army, Air Force, and Navy should be doing.

His still bigger fear is that, as the restoration sets in, the most creative and capable junior officers will leave the military out of frustration and boredom. These officers have led men and women in multiple combat tours, charted the boldest innovations, taken the most extraordinary risks, accepted the responsibilities and rewards. Yet when they’re rotated into a staff job, often in the prime of their professional lives, they find themselves trapped in a cubicle, reformatting PowerPoint slides and preparing quarterly readiness reports. “The consequences of this terrify me,” Gates said in his West Point speech.

Gates urged the cadets to take adventurous detours in their careers—go to graduate school, teach for a few years, become foreign-area specialists: in short, to broaden their perspectives, diversify their talents. Some of the most prominent officers of the past decade—Gen. David Petraeus among them—have done just that.

In 2007, soon after Petraeus took over the command in Iraq and shifted to a counterinsurgency strategy, Gates brought him to Washington to chair the Army’s annual promotion board. Several of the most creative colonels, who had adapted to the new strategy in Iraq with greatest success and innovation, were seeing their careers blocked by the traditionally minded generals who usually ran the promotion board (and who had no experience in this style of combat).

The Petraeus-run board (which was packed with other like-minded generals) rammed through the creative colonels’ promotion—and thus took the first steps at fomenting a cultural revolution within the Army.

On another front, Gates rammed through several weapons systems that he saw as vital to the war effort but that the defense bureaucrats were resisting. The systems included, most notably, new “unmanned aerial vehicles” (popularly known as “drones”) and a new armored troop-carrier, the MRAP, which provided more protection against the roadside bombs that were beginning to kill so many U.S. soldiers and Marines.

Gates told the Air Force cadets today that getting their top generals to go along with the drones in particular was like “pulling teeth.” (He didn’t tell them, though most of them must have known, that one way he finally got his way was to fire the Air Force chief of staff and replace him with an officer in more accord with Gates’ views—namely, Gen. Norton Schwartz, who rose through the ranks not as a bomber or fighter pilot, like every Air Force chief before him, but as a Special Forces pilot and head of the Transportation Command.)

In his four years as defense secretary, split 50-50 between Presidents Bush and Obama, Gates has managed not only to get these new kinds of officers promoted and these kinds of weapons systems funded and deployed—he’s also begun to see a broader acceptance of a new view of warfare and what kind of personnel, equipment, and training it requires.

But the reforms are far from complete, and, as Gates put it in his West Point speech, “the tendency of any big bureaucracy is to revert to business as usual at the first opportunity.” For the military, “that opportunity is, if not peacetime, then the unwinding of sustained combat”—which is already underway in Iraq and will be in the next few years in Afghanistan. If Gates really does leave this year, as he has said he’d like to do, then the first steps of this bureaucratic relapse could coincide with his last steps out the door.

Some in the defense world are incredulous that Gates might leave with so much of his legacy as yet unsettled. But part of this incompletion is of Gates’ own making. For better or for worse (and probably for a bit of both), Gates has never wanted the total overhaul that his rhetoric has at times suggested. As he emphasized in both of his recent speeches, he has never called for the elimination of heavy armor or fighter planes or aircraft carriers. To the contrary, his budgets have added, and continue to add, billions of dollars for these sorts of weapons. He has slashed or killed some of the services’ most cherished programs (the Air Force’s F-22 fighter plane, the Army’s Future Combat Systems, the Navy’s DDG-1000 destroyer), but he has boosted alternative programs that perform the same mission. He has pursued efficiencies, sometimes in rapier fashion, and he has forced the services to take on new missions. But he has rarely ordered them to drop the missions that they’ve long cherished.

He has always stressed—and did again in his two speeches to the cadets—that he is aiming for “the right balance” between what’s needed for “conventional” combat (which, though unlikely, may still happen decades from now) and what’s needed for the sorts of “irregular” wars that we’re fighting now and that we’re more likely to face in the near future.

But he hasn’t spelled out what the right balance is or how to go about calculating it. Perhaps it’s because he hasn’t figured it out himself (who has?). Perhaps, as a product of the Cold War himself, he can’t break away completely from that era’s assumptions. Perhaps the defense bureaucracy, against which he’s inveighed so often these past four years, is just too entrenched to challenge too much.

During an interview that I conducted last August for Foreign Policy, Gates noted at one point that, while he was cutting lots of Navy programs, he wasn’t cutting out any aircraft carriers. When I asked why not, he replied, “I may be bold, but I’m not crazy.”

In one sense, then, it’s a shame that Gates isn’t sticking around for another couple of years, until at least the end of Obama’s first term, so that he can continue grinding his reforms into the gears of the bureaucracy. He may be the only person with the experience and credibility to do this with the full backing of the president and at least the tolerance of Congress. It may be that a still-bolder defense secretary is needed to carry what Gates has done to the next stage. The problem is that, at this point, it’s just not clear who this figure might be.