During the two World Wars sexuality was fundamental to how both conflicts were planned, conducted, and experienced. The sexual body was an ever-present target of military policy as a potential polluter of the race, a danger to colonial order, sexual mores, or gender hierarchy; it was an object of intervention and mutilation, even annihilation. Nonetheless, war also offered opportunities for new, hitherto illicit sexual encounters. Individuals experienced sexuality in two opposing ways: as a source of immense suffering but also of erotic excitement and love. Changes in sexual attitudes, regulation, and practices must be understood through the filters of gender, class, race, sexual orientation, religion, and regional variations. Between 1918 and the `sexual revolution” of the 1960s a profound shift in sexual mores and attitudes took place in all bellicose nations. The millions of deaths on the battlefields, the suffering at home, the unprecedented mass movement within and between countries had sufficiently ruptured the social fabric to unleash a wide-spread liberalisation of sexuality. The steeply declining birthrate was the most dramatic expression of changing ideals. Yet, liberalisation was at best ambivalent as many traditional attitudes and regulations resurfaced and women and queer people struggled to fit back into a state-sanctioned `normal” life.