War and sexuality are indeed linked. Men are going to war, and are defending the country but also the "weakest", women and children. Men are asked to be viril and victorious. When German soldiers invaded France in 1940, they were seen as handsome, tall, pleasant. They were the victorious winners. French soldiers on the contrary, the "loosers", were described as dirty, tired and cowards. In the US, this description of French soldiers still resonates. The main reason: a very good propaganda from the USA. France was shown as a feminine country, emptied from men (more than 1 million were still in POW camps in Germany). The USA was the powerful and masculine country liberating France. When you look at magazines describing the Liberation, you will mostly see that the pictures show American soldiers surrounded by French women (even though there were still men in France). Back in the US, some American wives and girlfriends created associations and groups because they were afraid that their husbands/fiancés/boyfriends, would fly away with Frenchies.

On the other side, the French men who shaved French women because of their relationships with German soldiers (sexual relations mostly) were doing that as a revenge on the masculine condition they lost during the war. Shaving women was, for them, having back their masculinity/virility, but also punishing the women for being free with their bodies (apart from the women who were real collaborators or spies).

Everything in war tends to associate sexuality: viril men posing while saving the world, women waving tissues and waiting for them to come home, the phallic shape of weapons... primitive instincts tend to appear easily (in letters, in movies, in pictures...). Brothels were there to satiate these instincts and needs.

But the sexuality can also be violent. Rapes, humiliations, tortures (as well by men on men or by men on women) have always been used as a way to show a viril, masculine and victorious strength. Rape is considered as a massive "weapon" to attack indirectly troops. When a soldier hears that his sister has been raped by enemy troops, he wants to fight even more.

In the end, when men are coming back, there is that pleasant idea of the soldier returning home after saving the world or protecting his family... and therefore, nature is playing its part: babies are made. I am not saying that it happens to everyone but it is a widely spread society picture.

For more information on that subject, I strongly advice: François ROUQUET, Fabrice VIRGILI and Danièle VOLDMAN, "Amours, guerres et sexualité 1914-1945", Gallimard, 2007. And also: Mary Louise Roberts, "What soldiers do: sex and the American GI in WWII France", the University of Chicago Press, 2013.