The coronavirus pandemic has turned civilian life in the United States upside down — and there are changes underway for the U.S. military as the Pentagon addresses concerns that covid-19 may soon take its toll on U.S. military readiness.

These concerns are real — but there’s reason to temper the alarm. Here’s what you need to know.

What is military readiness?

The Defense Department defines readiness as “the ability of military forces to fight and meet the demands of assigned missions.” But the U.S. military’s ability to fight is not an end in itself — it’s also a tool the U.S. uses to influence how other countries think and behave.

For example, readiness may signal resolve — send a clear message to ally or adversary about U.S. willingness to fight — simply because the investment necessary for readiness is costly. U.S. allies confident in U.S. capacity and commitment to defend them may be more likely to hold off on taking measures like developing their own nuclear weapons.

Adversaries, meanwhile, might think twice before attacking a U.S. ally if the U.S. military demonstrates readiness to punish aggression. And if conflict does break out, readiness ensures the U.S. armed forces are well prepared to fight.

All this may seem intuitive, but it is actually quite difficult to measure the effect of military readiness on other countries’ perceptions and behavior. Accordingly, the Armed Forces usually measure readiness inputs with presumed links to readiness objectives. Broadly, these inputs are personnel, training, equipment and supply.

How the coronavirus may affect U.S. military readiness

Of course, military personnel have to be healthy enough to perform required missions. Military personnel are disproportionately young — which seems to put them at lower risk of serious infection and death from covid-19 than the average civilian. But many military personnel live in close quarters — ideal conditions for the rapid spread of infection.

Military discipline, however, makes implementing social distancing easier. The Pentagon has already begun restricting movement, prohibiting gatherings and minimizing the training and exercises that put service members in close contact. For example, major troop exercises often draw in service members from widely dispersed locations. Reducing the size and frequency of domestic training and multinational exercises may be one way to slow the spread of the infection.

But these measures will come with costs. Training reductions could leave healthy personnel less ready to perform their missions. While some training could be eliminated with little consequence for readiness, other reductions would quickly compound. As one analyst notes, “Artillery school students need to shoot on the ranges. Paratroopers need to jump out of airplanes. If that kind of training stops, units will quickly lose their edge.”

Trained personnel cannot fight and equipment breaks down without supplies like food, fuel, ammunition and spare parts. Covid-19 has already disrupted some global supply chains as factories have closed and transshipment has been affected.

These problems may worsen if U.S. manufacturers and transporters slow operations. The scale of disruption and size of military stockpiles will determine when these effects are felt, but the deeper the Department of Defense digs into its stockpiles, the longer it will take to rebuild them later.

Modern armed forces rely heavily on complex equipment like ships, tanks and aircraft that require significant maintenance to function properly. The “depots” for this deep maintenance are already in poor condition — at some facilities, inexperienced workforces have trouble completing maintenance without widespread delays. Covid-19 could worsen these delays and make depots fall further behind. There is currently little slack when it comes to the readiness of the U.S. maintenance base system.

What does this mean for U.S. national security?

Fundamentally, military readiness is a means to an end: U.S. security. High readiness can signal capability and resolve and may help assure allies that the United States won’t abandon them. And a fully operational and ready military may deter potential adversaries from taking aggressive action. However, the key ingredients for effective deterrence and assurance remain highly debated in academic international relations, and academics often overlook the specific role of military readiness in deterrence and assurance.

Nonetheless, a decline in readiness caused by a pandemic may have less impact on the perceptions and behaviors of allies and adversaries than a similar decline caused by other factors. Here’s why:

First, a pandemic-induced readiness decrease is less likely to be interpreted as a weakening in U.S. resolve than a decline in readiness caused by other factors under U.S. control — like budget cuts or deliberate reallocation of resources from one theater to another.

Second, adversaries will likely understand that the pandemic would not stop the United States from responding to aggression. Armies have long braved the risks of disease for the sake of battle, and adversaries would likely conclude that concerns about the virus would take a back seat if territorial aggression occurred.

Third, when it comes to security competition and war, everything is relative. The U.S. military is not the only force having to deal with the coronavirus outbreak. Two relative measures matter: relative readiness pre-virus, and relative readiness decline due to the virus. In general, the U.S. military maintains a better trained and better supplied force than its potential adversaries — which means the United States starts from a higher readiness baseline.

Of course, because the United States gains an advantage from its superior training, extensive training reductions could affect it more than other forces. That said, the coronavirus pandemic has also reached many potential U.S. adversaries. China and Iran were early centers of the outbreak, and while little is known about the spread of the virus in North Korea, the regime might think twice before exposing its forces to the significant outbreak in South Korea.

The coronavirus pandemic will continue to negatively affect U.S. military readiness, leaving the Pentagon to think carefully about how to mitigate the impact on training and overall troop readiness. But after investing heavily in its military, the United States enjoys a surplus of power and redundancy in its tools of influence — and this may buy some peace of mind in moments of global turmoil.

Rachel Tecott is a PhD candidate in political science at MIT. Her research examines military strategy, security force assistance and civil-military relations.

Erik Sand is a PhD candidate in political science at MIT. His research examines great power dynamics, bureaucratic politics and the intersection of strategy and economics.