During the AI-wars there were a lot of human casualties so the Army needed a lot of soldiers.
Before this war started, gene-technicians had already 'created life' in a petri dish, gestating humans to use as cheap labour. Thus a whole new human race was created, which is since then known as InVitros.
After the artificial fertilization in petri-dishes the embryo is put into an artificial gestation chamber (a tank) and the IVs are taken out of the tank ("born") when they reach the age of 18 years. They are trained in IVA Facility Centres and are strictly kept away from natural born humans. The training is for duty in the military, in mines and other places in human society which are thought too dangerous for natural borns.
Since the InVitros have no physical parents to supervise their upbringing and have never had the benefit of a loving family they have developed in socially mal-adjusted individuals. They have neither a need to protect their kin (as they have none), nor do they have any sense of patriotism.
During the AI-wars they fought instead of the usual human soldiers, but many didn't want to after many casualties among them became known. The InVitro units of the military was eventually disbanded.
Natural born soldiers still had to fight in the AI-war and many of them died. This created a new form of racism. The Invitros were called tanks or nippel-necks. They were considered to be lazy and not patriotic enough by the racists.
InVitros have a navel or omphalo at the back of their necks, immediately making them recognizable as InVitros.