You highlight the fact that not every situation is the same. So, do you agree with a blanket condemnation of combat military service for Christians?
No
How honestly is the combat Xian soldier any different than Xian police officer? Sure the officer has a more peaceful territory and might have broader peaceful options in subduing a threat but ultimately they have the same authority and same duty which is to make sure things are safe.
How is tthe man in a defense situation doing anything that a good father and husband wouldn't do to protect his own! How would it sound if a man allowed an intruder to harm his wife and children under the arguement of turning the other cheek? It would seem really ridiculous! Being slapped on the cheek is an act of insult or humiliation not imminent danger of full bodily harm or death!
This said a Xian combat soldier would hopefully be mindful of his responsibilities as a Xian and execute his orders without becoming frenzied or blood thirsty! Further a Xian would probably discern the greater damage to the enemy camp by wounding versus killing. Live bodies require attention and resources while the dead often times become birdfood on the battlefield. I also know many men who are or have been at the front lines discern fully that neither he nor the enemy really want to be their on the field versus at home with family. Each have a cause to further, it isn't personal. And for many who the US would label an 'enemy' they are just poor schmucks who are there out of required national enlistment or because his leader who wasn't democratically elected by him or anyone else is commanding him into combat.......that said just because a man is in combat doesn't mean he has to do his best if he feels the fight is immoral..... people can intentionally miss their targets.
Now that said all Xian men are not the same so some will have a better talent for being able to handle himself than another.
The truth is I never think about 'greater' defense because I live in a paternal society in which my forefathers have set about structures to keep us women folk protected (whether that be in a tribe, nation, state, county, city, or congregation)........