It is official: Gen. James Mattis, USMC ret., is President-Elect Trump’s nominee for secretary of defense. Although many national security professionals in the know breathed a sigh of relief, others pulled the alarm on civilian control of the military. It is not good, the argument goes, for general and flag officers to assume the role of civilian leadership when the shine has not yet worn off their stars. But Mattis is so good, others argue. We might have gotten stuck with an ideologue or an outright neophyte. And he even wrote a book on civil-military relations! Surely, one of our most expert warrior-scholars is superior to the other possibilities.

That is probably so. And being a pragmatist, I will stipulate up front that of the names floated for SecDef, I like Mattis the best. He is expert, thoughtful, experienced, tough, smart, and savvy. So, I am not especially worried about how Mattis the man will handle the job. I am far more worried about how the military as an institution will respond and what comes after Mattis.

One of the reasons for the statutory seven-year separation between military retirement and senior civilian appointments is to allow for some meaningful distance between the officer and his or her service. Civilian leaders are meant to operate based on the national interest rather than parochial service interests. Lawmakers were trying to avoid a situation where, say, Army preferences become overall Defense Department preferences, or, for example, budgetary trade-offs favor one form of warfare over another. There is a reason that sub-specialty communities get excited when one of their own ascends to the spot of service chief: There is expertise and affinity there, not to mention a network of people to whom one owes loyalty and consideration. This is only human, and there is nothing particular about military officers that makes parochialism more likely. The same concern applies for civilian leaders’ relationship with previous employers, a concern that has spawned a series of ethics laws and standards for former lobbyists and defense industry alums in particular.

For the secretary of defense, the principle of reflecting national rather than parochial interests should translate into impartiality between the services. Mattis only retired from the Marine Corps in 2013 which means he is being named four years before the wait time is up. The wars in which he commanded troops are still ongoing. Many of the senior officers he served with are still in leadership positions. His military family is still in the building. Again, many others have argued that Mattis is an independent personality who will not lie prone before quotidian civil-military issues. He will likely use civilians in the Office of the Secretary of Defense to formulate his judgments about the use of force, weapons sales, and force structure decisions. When civilian advisers oppose Central Command proposals or Marine Corps projects, he will probably exercise his famous capacity for getting to the heart of an issue, regardless of whose feathers are ruffled. But the point is not really about Mattis but about the precedent. And even if a Secretary Mattis is able to put some objective distance between himself and his former service, some in the Corps may well feel like they are first among equals. Already, Marine Corps Special Operations Command posted (and then removed) a celebratory ode to “Saint Mattis” on their Facebook page. It’s a silly example, but its implications are serious. Other services might start to consider whether they should grow one of their own to ascend the top post someday. Perhaps, these possibilities are remote. I believe we can trust members of the U.S. military to remain more committed to a professional ethos than most everyone else in Washington. But if political science teaches us anything, it is that institutions will protect their interests. Why wouldn’t we expect the services to seek favor wherever it is available?

This leads to the other, perhaps more important, reason to be concerned about recently-retired general and flag officers running major elements of the government: the politicization of the military. This may happen in two ways. First, the military may begin to become associated with one party over the other, robbing the profession of its historic political impartiality. Trump already claimed during his sit-down with The New York Times that the majority of the military voted for him. Now, by trading on the legitimacy of military officers in senior positions, the president-elect is attempting to align the military as an institution with his own political fortunes. Former Chairman of the Joint Chiefs of Staff General Martin Dempsey warned his fellow four-stars about such a possibility last August, observing that retired officers’ political endorsements are valued because they appear to represent those in uniform as a whole. Writing almost 17 years ago in The Washington Post, Richard Kohn observed:

A politically conscious military appears to be just one more pressure group acting to advance its views and interests, not the neutral institution of the state and the embodiment of the nation.

Even though the vision of widespread military preference for a particular president or party is probably more optical than real, it could still generate unnecessary tension between the services and current members of Congress, not to mention future presidents.

Second, active-duty officers may begin to view political appointments as natural addenda to their careers — rather than the rarity it is now — encouraging partisan ambitions prior to retirement. If this happened, it would seriously undermine civil-military trust by introducing the specter of political competition into the relationship. Promotions and appointments based on political loyalty rather than professional skill could begin to erode “the quality of advice.” Open partisanship could also threaten the cohesion of the force. Precisely because the military is not a monolith, such an eventuality could not only cause divisions between senior military leaders but within the ranks as well.

None of this is or would be nefarious or even intentional. Human beings simply respond to incentives, and military officers in particular respond to the combination of duty, responsibility, and patriotism. If generals like Mattis continue to be, objectively, among the best available (and willing) candidates for civilian leadership positions, they are very likely to take them on for the good of the country they have spent their professional lives protecting. But in the long run, the outcome for both our military and our politics will not be good at all.

Alice Hunt Friend is a Senior Affiliate at the Center for a New American Security and the Center for Strategic and International Studies and was previously Special Adviser for Strategy, Plans, and Forces and Principal Director for African Affairs in the Office of the Secretary of Defense. The views expressed here are her own.