Fraternization happens all the time in the military. But there is something unusual about “improper relationships” between men and women in combat arms units, where there were no women until the Pentagon formally eliminated gender restrictions in 2016.

In September, we heard about two separate incidents, one in the Army and one in the Marine Corps.

In the Army’s storied 82nd Airborne Division, a company first sergeant was disciplined for having an affair with a private first class who had just arrived at the unit. She was among the first enlisted female soldiers to graduate from the Army’s infantry basic training.

Both soldiers were disciplined. The Army did not disclose specifics, but neither lost their rank, and it appears both remain in the Army.

In the Marine Corps, however, one of the first women to enter the infantry is now facing separation because she was fraternizing with a lower-ranking Marine in her unit. Initially a sergeant, she was busted down to a corporal, and now the commanding general of the 2nd Marine Division is deciding whether to force her out with an other-than-honorable discharge.

It’s worth noting that the Marine, now-Cpl. Remedios Cruz, eventually married the Marine with whom she was carrying on this improper relationship.

It looks like the Army and Marine Corps have handled similar situations very differently.

Cruz’s attorney lauded her as “a courageous pioneer for women in the military and she has earned a place in Marine Corps history.”

But Cruz’s career is over. And it looks like the Corps is going to send the 26-year-old New Yorker away with a DD-214 that will be a red flag for the rest of her life.

The Corps’ handling of the matter raises questions about fairness.

Would Cruz be facing an other-than-honorable discharge if she were not among the “courageous pioneers” for women in the infantry? Is there political motivation underlying the decision to highlight this incident with distinctly heavy-handed punishment?

The Marine Corps as an institution has made no secret of its reluctance to integrate combat units in accordance with the Pentagon’s 2016 policy.

In all the services, fraternization happens all the time.

When it fosters the appearance of favoritism, it can erode morale and unit-cohesion, which is, arguably, especially important in the combat arms.

But the military’s prohibition on fraternization should be enforced fairly, regardless of gender. There’s no reason to think women should face any more or less punishment for fraternizing.

In some cases, it’s perfectly appropriate for a commander to dole out a harsh punishment in an effort to “send a message” to the unit.

But if the Corps was trying to send a message with its handling of this case involving Cpl. Cruz, that’s an ugly message.