Really dumb and shortsighted. Coronavirus vaccination rates in the military are extremely high, so this won't have much effect in the short-term. But it isn't good for the future in a coronavirus pandemic that could always evolve negatively. And this sets a really bad precedent for military vaccination mandates in general.
Only 8k servicemen got discharged for refusing to get the vaccine. Republicans that argue the mandate was harming recruitment are tilting at windmills.
The military has required the annual seasonal flu vaccine since its creation in 1945. Depending on theater of deployment, some servicemen get the smallpox vaccine still despite its global eradication- a vaccine that carries a more severe side effect profile than the coronavirus vaccine. So spare me on this being a question of benefits versus costs.
Arguably the moral justification for vaccinating the military is as strong as healthcare professionals, even beyond troop readiness- they are in foreign countries, often working in close quarters with vulnerable people. That is of course part and parcel of why they get so many vaccines that the general public doesn't get. It is a foundational concept in our nation's history. George Washington ordered all his troops to be inoculated for smallpox during the Revolutionary War.