All who desire to serve their country in uniform are to be commended. That includes transgender individuals. Too few Americans wish to serve.

Of course, not all people willing to serve are able to do so. Today, only 25 percent of U.S. citizens aged 17-24 meet military entrance criteria. The most common disqualifications are physical fitness issues, including obesity, medical issues, lack of high school education or criminal records.

These standards serve two essential purposes. They help ensure that those entering the armed forces will be able to successfully complete their term of enlistment in what is one of the most physically demanding and arduous professions in America. And these standards reduce the risk that military service will cause harm to enlistees.

For example, an individual who wants to enlist but who has moderate asthma would be ruled ineligible for two reasons: He may jeopardize an entire unit's success by not being able to contribute at a critical moment, and also because – without access to proper medical treatment – he may become a casualty.

From 2001-2003, I served as an army brigade commander. In that position, one of my responsibilities was to oversee basic combat training. The rigorous training often exposed medical conditions that had gone undetected during entrance examinations. I had to make daily decisions on whether individuals in training should be retained or released.

Typically, these new soldiers desperately wanted to stay in the service despite their disqualifying medical condition. "Isn't there a desk job in the rear where my medical condition won't matter?" they would ask.

Unfortunately the answer to that question, which must be the same in all the services, is "no."

Every soldier, every service member, must be ready at a moment's notice to deploy to a distant hostile battlefield, away from family and support, to fight and win. There is no guarantee of a continued supply of medication or medical treatment in these remote areas. And success depends on every person doing his or her job.

At the July 2016 press conference announcing his decision to open the military to transgender individuals, Ashton Carter, President Barack Obama's Defense Secretary, spoke eloquently about clearing away barriers to service.

But rational recruiting standards must be established and enforced strictly to assure that our military can meet readiness requirements and to protect at-risk citizens from being harmed by the demands of military service.

I'm just a former soldier, not a doctor, but I am aware of survey data that indicate some 40 percent of transgender individuals attempt suicide in their lifetimes – nearly nine times the attempted suicide rate of 4.6 percent in the U.S. population as a whole.

In that same survey, 39 percent of transgender respondents reported that they had experienced serious psychological distress in the month prior to completing the survey, compared with only 5 percent of all respondents.

I can think of nothing more stressful and more likely to exacerbate a pre-existing psychological distress than combat deployments to inhospitable places.

For the first time ever, at least in part due to the stress created by more than 15 years of continuous warfare, the U.S. military is coping with a suicide rate higher than that of the general population.

It would be both reckless and immoral to allow transgender individuals to enlist in the armed forces before we have fact-based assurance that they have the mental resilience needed to survive the crucible of combat and deployments.

Before President Donald Trump's tweets about prohibiting military service by transgender individuals, Defense Secretary James Mattis had announced a six-month pause in the implementation of his predecessor's policy in order to assess its impact on military readiness.

Such caution and prudence seem to be the best policy option until the complete impact on readiness can be determined.