COLORADO SPRINGS – Three soldiers in camouflage huddled around a table at a popular burrito restaurant near Fort Carson on Friday, chewing over the announcement that the military could soon vaccinate all troops against coronavirus. Two of the soldiers had already received the shot. One didn’t have it.

The military had ordered her to be given a quiver of other vaccines, including the annual flu shot. The big difference to this one was that she finally had a choice.

“Honestly, if the Army wants something from you, they’ll force you. It was still voluntary, so I just postponed it, ”said the unvaccinated soldier, adding that a busy schedule and fear of side effects made her delay easier.

The soldier declined to give her name because she was not allowed to speak to the news media, but said that although most of the soldiers in the post’s 25,000 active soldiers are vaccinated, she has other concerns and takes advantage of a rare digression not often granted the base.

That may change soon. Late on Thursday evening, the Pentagon announced that all military and civilian employees would be asked to prove that they were vaccinated or undergoing masking, physical distancing, and regular tests and travel restrictions, just as President Biden would do with the rest of the citizens. The new requirements bring the armed forces one step closer to a mandate.

Forced syringes are a standard practice for the military, requiring from training camps that troops be vaccinated against at least a dozen diseases. For now, however, the military is trying to navigate how more troops can be fired without simply issuing an order.

Of the 1,336,000 active military personnel, about 64 percent are fully vaccinated, and more than 60 percent of Americans over 18 are fully vaccinated. But for the military, that quota is unacceptably low because it is difficult to send unvaccinated troops to countries with strict local restrictions, and because an increase in the virus among troops can cripple readiness.

Military leaders cannot request the shots because the coronavirus vaccines are not fully approved by the Food and Drug Administration and are only approved in an emergency. Mr Biden could order mandatory vaccination for troops but was reluctant to exercise that power, and Secretary of Defense Lloyd J. Austin III previously said he would not be comfortable with a mandate until vaccines are fully approved.

Although coronavirus vaccines have become a political focus among civilians, several military leaders said they did not expect much resistance if an order was issued because troops are used to getting mandatory shots. But while following orders is central to military culture, they added, the soldier’s axiom is “never voluntary for anything” as well.

At the same time, the U.S. military knows how deadly infectious diseases can be because it has fought them for centuries.

In the winter of 1777, the Continental Army’s smallpox was so raging that the ability to continue the fight was in doubt. General George Washington proposed the very first mass vaccination by infecting healthy troops with the pus of their suffering comrades. The practice, which often led to illness but drastically reduced deaths, profoundly polarized. Many colonists viewed it as a conspiracy of the devil, or worse, the crown. Some colonies banned the practice, and in Virginia rioters attacked doctors who offered the treatment.

However, Washington felt it had no other choice, telling one of its medical officers that “the need appears not only to approve but to require the measure.”

Mass vaccination ended the epidemic and may have been crucial to winning the war, said Carol R. Byerly, military medicine historian.

“It was the beginning of the realization that public health is a strategic weapon – and the military has led the way ever since,” said Ms. Byerly.

As new conflicts pushed US forces into new corners of the world, disease often killed far more people than the enemy. Military doctors tried to find ways to fight diseases like typhoid and yellow fever. The troops, some of which served as guinea pigs, were generally not given a say.

“There has always been protest,” Ms. Byerly said, referring to the year 1911, when many soldiers and their families launched a letter campaign against a newly developed smallpox vaccine, which became the first universal, compulsory vaccination in the army. “But the military knows that vaccines are the best weapon. Even if there is controversy, the leaders thought it was worthwhile. “

The ordering of a mandatory vaccination, however, carries its own risks for the military readiness. By the 1990s, the military grew tired of vaccinating the entire force against the anthrax virus. Troop units refused to comply. Hundreds were fined – some with dishonorable layoffs. Others quit in protest. In one Air National Guard squadron, a quarter of pilots dropped out instead of taking the vaccine, affecting the unit’s operational capability.

Anthrax vaccination efforts have been hampered by legal proceedings and supply problems and ultimately reduced to just a small fraction of the high-risk troops.

Without an order, the service branches attempt to encourage members who are hesitant to take the coronavirus vaccine in a way that they believe addresses their specific concerns.

Naval leaders have found that talking about the vaccine as both a weapon and a means of preparedness is most effective. “Our sailors understand that they must wear protective equipment when walking into a hostile or dangerous environment,” said Rear Adm. Bruce L. Gillingham, the Navy surgeon general. “It’s biological body protection.”

In Fort Bragg, NC, a weekly podcast featured troops speaking to Army medical leaders about their concerns about the vaccine.

In a recent interview, Sgt. Colt Joiner and Lt. Col. Owen Price discussed a misconception often raised by young soldiers: that they are at greater risk of dying from the side effects of a gunshot than from Covid-19. This belief is increasingly worrying military commanders as data on the delta variant show high rates of serious illness in young unvaccinated people.

“I’m a 24 year old guy,” said Sergeant Joiner, “I think this isn’t such a big risk for me right now. At the moment I just don’t see it as a priority. “

The notion that the coronavirus is a threat only to older Americans is “eroding,” Colonel Price told him. “The percentage of people your age who see these effects is increasing.”

In Fort Carson this week, an officer in a brigade preparing for the mission proudly said their vaccination rate was 71 percent, well above the Army average. Success, he said, means taking leadership – getting senior soldiers and officers, explaining their choices to the young soldiers, and encouraging them to volunteer.

But was that volunteering actually “volunteering” – the army’s cherished tradition of telling the troops that they are absolutely expected to do something that is technically voluntary?

When asked, the officer laughed. “Yes,” he said. “Probably a little of that.”

Dave Philipps reported from Colorado Springs and Jennifer Steinhauer from Washington.