The first few hundred U.S. troops arrived along the southern U.S. border Friday, just days after President Trump’s announcement that active duty forces would now join U.S. Customs and Border Protection (CBP) and National Guard units already there. On Oct. 29, the Pentagon announced that some 5,000 troops would head to the border — a move that includes “air and ground transportation and logistics support,” “combat engineering battalions” and “medical support units,” along with surveillance technology and expeditionary housing for CBP personnel.

The U.S. government hopes, it seems, that the “show of force” will dissuade the caravan of 3,500 to 7,000 migrants marching through Central America into Mexico from attempting to cross into the United States.

Critics accuse the Trump administration of “wagging the dog,” using the military to concoct a threat that will galvanize Republican and swing voters days before a highly contested election — the president himself calls the midterms a “referendum” on his performance in office. Supporters contend the military presence is necessary to defend U.S. national security and sovereignty.

Americans count on an apolitical, nonpartisan military to help maintain our democracy. Here’s why this deployment raises concerns that the military is being drawn dangerously far into politics:

1. This level of deployment has no operational rationale

Military forces clearly overmatch the migrants. Combining the initial projection of 5,200 fresh troops with the previously deployed 2,092 National Guardsmen renders a troop-to-asylum-seeker ratio of almost 2 to 1, and the ratio may grow larger as weary marchers peel away from the caravan.

Even with its hiring problems, the Border Patrol’s firepower, logistics, mobility and communications — even without the reinforcements — far exceed the capabilities of the group of individuals and families traveling on foot, who perhaps have cellphones and clothes but little else.

2. Americans think highly of the military — and politicians know this

This isn’t the first time the military’s credibility with the American public has been used to underwrite electoral goals. And the social desirability of supporting U.S. troops means that they can be used as human shields against political criticism. But debates about the operational logic of this deployment obscure the more profound effect such decisions may have on the military’s domestic political role.

The military is one of the few institutions a comfortable majority of Americans still admire — military approval has not dipped below 70 percent in the past 10 years. Trump counts the military among his supporters and surrounded himself with retired and active-duty general officers early in his administration. He boasted after the 2016 election that the military voted for him overwhelmingly and rallied audiences on military bases to shout anti-media chants.

3. Deploying the military on domestic soil has long been controversial

Trump’s border moves have generated considerable controversy among military veterans.

Throughout U.S. history, civilians in and out of government have generally acknowledged that neither service members nor politicians should use the military as a domestic coercive or policing instrument. This is explicitly forbidden by the Posse Comitatus.

Why is this a worry? In the extreme, routinizing the use of the military to advance political goals raises concerns about a slippery slope toward political violence and even coups. If officers and their institutions are used to legitimize a domestic political agenda, partisans eventually could threaten opponents with force, not just electoral losses. Coups evolve when the military itself, in an effort to protect its own interests, uses its coercive power to assume control of the government.

Have Americans ever had to seriously worry about a military coup? Thankfully the answer is “no.” Moreover, Posse Comitatus prevents domestic uses of military force, and presidents tend to refrain from using the military in ways explicitly tied to elections.

4. The scale and timing are what make this deployment different

There have been cases where presidents deploy forces in election years — including deployments of troops to the southern border by George W. Bush and Barack Obama in midterm years (in 2006 and 2010, respectively).

What makes this troop deployment different is not only the scale, which Trump seems to be ratcheting up daily, but also its timing immediately before the midterms and its political context.

Trump’s decision midweek to deploy even more troops — “anywhere between 10,000 and 15,000 military personnel” — likely cues off polls showing Republican voters have concerns about immigration. The administration has been arguing for weeks that immigrants, and the migrant caravan in particular, are a threat. “This is an invasion of our Country and our Military is waiting for you!” was the message in one presidential tweet. The president blames Democrats for lax immigration policies and lax border security.

The migrant caravan is some 900 miles — or 300 hours of walking time — south of the most southern section of the U.S. border. Militarizing the southern border over the past week appears to be a dramatic gesture to heighten the perception of public threat, and perhaps rally Republicans into voting booths on Tuesday.

5. In a polarized age, the deployment risks further politicizing the military

Candidates for high office have sought officer endorsements for years, including during the last election cycle. Critics argue that deepening the military’s role in electoral politics promotes narrow rather than national interests. If such abuses continue, the military could become affiliated with one party — or become a political tool for whichever party occupies the position of commander in chief.

The public foundations for this outcome are already in place. In a paper presented at the American Political Science Association meeting this August, Peter Feaver and Jim Golby observed that their surveys and others show “public confidence in the military is significantly conditioned on partisanship and political ideology.” In other words, a person who identifies as a Republican has, on average, far more confidence in the military than someone who identifies as a Democrat. But Golby and others also found that strong partisans in the United States express greater confidence in the military when a member of their own party is president — and Democrats’ confidence in the military increases especially dramatically when a Democrat is president.

For Americans’ faith in their armed forces to shift with the political fortunes of their own party is something to be concerned about, potentially politicizing the military and bringing a civil-military dynamic that is unhealthy for U.S. democracy.

Alice Hunt Friend is a senior fellow at the Center for Strategic and International Studies and a PhD candidate at American University’s School of International Service. She was the principal director for African Affairs in the Office of the Secretary of Defense from 2012-2014. Find her on Twitter @ahfdc.