In the face of any conflict throughout history, those preparing to go to war tend to do certain things to "tie up loose ends" in the peaceful lives they are leaving behind. For many men preparing to become fighters involved in a war, one of those activities may involve getting married to the girlfriend he will be leaving behind.
This statement of commitment carries many levels of meaning and importance. It is an indication of the feelings the husband and wife have for each other and a promise that those feelings will continue regardless of the war's impact. It is an expression of hope that the husband will return from the fighting to continue life with his wife after the war. If the couple did not engage in premarital intercourse, the marriage before the husband departed allowed them some short period of time in which they could enjoy this benefit of marriage.
Becoming a wife instead of a girlfriend also gave the woman a different status. If the man was killed, the wife was entitled to different benefits as surviving spouse than would be available to a girlfriend. Wives were more likely to be allowed to visit injured husbands in hospitals than were girlfriends. The mutual support women gave each other on the home front was more organized and had greater depth for wives than for girlfriends.