Should military officers like Jim Mattis enter the political arena?

Without saying anything about the presidential campaign, retired Adm. Mike Mullen, former chairman of the Joint Chiefs of Staff, and former Defense Secretary and retired Marine Corps Gen. Jim Mattis became the center of the political conversation last week when they denounced President Donald Trump. Although Trump has courted military men and placed them in his Cabinet, his disregard for the law, his divisiveness and his erratic nature rub many, like Mattis, the wrong way.

On Wednesday, the general wrote: "When I joined the military, some 50 years ago, I swore an oath to support and defend the Constitution. Never did I dream that troops taking that same oath would be ordered under any circumstance to violate the constitutional rights of their fellow citizens — much less to provide a bizarre photo op for the elected commander in chief, with military leadership standing alongside." He lamented that Trump was the first president in his life "who does not try to unite the American people." Instead, "he tries to divide us."

Trump responded by calling Mattis "the world's most overrated General" and noting that he was happy that the general "is gone."

This back and forth reflected the key role the military has come to play in politics, campaigns and elections today — and likely will play as 2020 continues.

But that obscures how new this role is. Retired military officers have regularly offered presidential endorsements over the last three decades, but the first in the wave of such endorsements didn't come until 1988 when retired Marine Corps commandant P.X. Kelley came out in favor of George H.W. Bush. As mundane as it feels today, this practice reflects something quite dangerous — the increased politicization of the military and the reliance of civilian politicians on the armed services for credibility.

The most interesting and significant endorsement of a candidate by a retired military officer occurred in 1992 when a former chairman of the Joint Chiefs of Staff, retired Adm. William Crowe, endorsed Bill Clinton and served as an adviser to his campaign. Crowe's endorsement was highly controversial: Some saw it as a way for him to generate news coverage about something other than the Iran-contra scandal in which he had been implicated. For the Clinton campaign, however, Crowe's involvement was a long-lasting project that served multiple functions.

The Republican Party had succeeded in the 1980s in branding itself as the defender of the military and painting Democrats as peaceniks. The culturally divisive Vietnam War and George McGovern's unsuccessful 1972 challenge to Richard Nixon had begun splitting the parties along these lines. Jimmy Carter's lackluster foreign policy, culminating like his presidency in a sense of impotence over the Iran hostage crisis, fed into Ronald Reagan's bellicose Cold War saber rattling and bolstered military spending.

The divide only grew as Republican campaigns presented Democratic candidates as liberal, intellectual and, above all, soft. In 1984, Walter Mondale ran against Reagan on a platform that included support for a nuclear freeze. Perhaps the nadir: Michael Dukakis in 1988 infamously tried to demonstrate his commander in chief chops and shed his party's "soft" label by riding in a tank and instead ending up looking ridiculous.

In 1992, Les Aspin, the Democratic chairman of the House Armed Services Committee, argued that any Democrat needed to pass through "a gate in the electorate's mind labeled commander in chief," which could be accomplished by demonstrating "knowledge and toughness." Clinton adviser Richard Holbrooke was particularly insistent that the American electorate would back the candidate that they felt was "toughest" in a general election. But this was a high bar for Clinton, who had not served in the military, was accused of being a draft dodger and faced off against Bush, a war hero.

Crowe's presence was designed to signal that a distinguished military officer believed Clinton had what it took to be commander in chief. By the summer of 1992, the admiral was serving as a campaign adviser, helping to formulate Clinton's nascent defense policy and trying to provide guidance on the potentially explosive issue of allowing gay people to serve openly in the military (resulting in the "Don't Ask, Don't Tell" half-measure).

The sense that Clinton was fighting an uphill battle to demonstrate his fitness to lead the military led to Crowe taking on a major role in the campaign in a way that no former top military official had in recent American politics. (While former generals from George Washington down to Dwight Eisenhower had entered politics themselves, they had not usually backed others as military advisers.)

Crowe came out publicly in favor of Clinton at a carefully crafted media event on Sept. 19, 1992. Crowe's statement included a number of now-familiar themes, notably his emphasis on the idea of "leadership." Crowe explicitly tackled the question of Clinton's lack of military service, saying that it was not the uniform that determined one's capacity for leadership. Crowe became an integral part of the campaign, something more significant and unprecedented than other military endorsements, except perhaps for Colin Powell's endorsement of Barack Obama in 2008 (which was different because Powell was a former Republican secretary of state as well).

Crowe's endorsement signaled to other military officers that it was OK to hop on board. Over the next month, Clinton accumulated the endorsements of 21 other generals and admirals, allowing Crowe to position his ongoing endorsement as a reflection of broader, confirmed opinion. This push also started the trend of the numbers count, in which each presidential campaign jockeyed to see who could secure more endorsements from retired military leaders.

A perfect storm produced Crowe's endorsement: the precedent set by Kelley in 1988, Crowe's desire for a renewed and more positive public role and Clinton's needs as a candidate. But it was also the result of two significant longer trends in U.S. history, the beginning of a widening gap between civil society and the military after the end of the Vietnam War and the end of the Cold War, which created the opportunity for an inexperienced candidate like Clinton. That Clinton was successful, and that this success could in part be credited to Crowe's vouching for his toughness, made military endorsements an important element of presidential campaign strategy.

Not surprisingly, once this habit was established, such endorsements skyrocketed, peaking with the 500-plus retired military officers who backed Mitt Romney's unsuccessful 2012 campaign.

Such endorsements became pivotal because of broader currents in American history: While every president from World War II until Clinton had served in the military, no recent president has had significant military experience (George W. Bush served in the Air National Guard and saw no combat). And that matters because American civil society has grown increasingly distant from its soldiers, requiring candidates to reach across this divide, especially since the military is the public institution that garners the most respect. Candidates seek out military endorsements as a way to attach the well-respected military brand to themselves, as well as to use such endorsements as a bridge to the military.

Trump — obsessed with toughness and lacking a military record — gravitated toward this practice, going even further than Bill Clinton, as evidenced by his decision to put two retired generals in his Cabinet and appoint a third as national security adviser. He's seeing that potentially backfire as Mattis now blasts his handling of the uprisings in the wake of the police killing of George Floyd. Biden, in turn, will undoubtedly chase such endorsements, seeing them as a symbol of Trump's failing on foreign policy and national security, and a sign of the Democratic Party's ability to keep Americans safe.

But national security experts worry that these endorsements may make the military less independent and trusted, potentially even preventing the military from acting efficiently because politicians worry about generals' political motivation. The very divide between those who see endorsements as appropriate, maybe even necessary in trying political times like ours, and the military leadership fighting to retain an image of nonpartisanship creates unnecessary tension within the armed services.

A politicized military, or even a military perceived as having partisan political interests, could be sidelined if its advice is no longer seen as neutral — something that seems an even greater risk after Trump's use of the military last week. Even the hint that the military is politicized in a partisan way could also create more cynicism about decisions of war and peace in an already skeptical public.

So as much as Trump opponents cheered Mattis' statement, and retired military officers will probably play a further role in the 2020 campaign going forward, it could do more damage than good.

Stricof is a doctoral candidate studying American history at Aix-Marseille Université. He wrote this for The Washington Post.