What was done to make them into soldiers?

In Chapter 12, the lieutenant gathers everyone in the village to the central square. There he informs them that the rebels are near and the military needs the help of able-bodied men or boys. He says those unwilling to join the military are free to leave, but they will have no more food or supplies from the village. The boys discuss their options and realize they only have one choice: join the Sierra Leonean army. To leave the village is to die.

The next day the lieutenant shows the villagers the mutilated bodies of a boy and a man. He informs the villagers that the two attempted to leave the village freely, but the rebels captured, tortured, and killed them. The lieutenant insists that this behavior shows the evil of the rebels and the need for good people to stand up against them.

Girls and women were then sent to help in the kitchen, while boys and men are sent to the ammunition depot. Beah receives his weapon, an AK-47, and trembles with fear the entire time he holds it. The soldier distributing weapons encourages the new recruits that they will soon learn how to use this weapon to kill rebels. That night, Beah notices first that his former traveling companions have no desire to speak with one another (they are in different tents) and second that he is awake without a migraine for the first time in weeks.

The next morning the boys are summoned from their tents early to report for training. Beah helps his tent-mates to get out of bed and get into file. They exchange their old clothes for new shoes, army shorts, and t-shirts; in the process, Beah’s precious rap tapes are thrown in the fire with his old shorts and destroyed. Beah learns that his tent-mates, Sheku and Josiah, emulate him rather than their commanding officer since they see him as an older brother figure. Their young commander, Corporal Gadafi, puts them through their paces practicing running, crawling silently, and recognizing hand signals so that they will not give away their positions in the forest by speaking. He rushes them through their breakfast in order to train them to eat within a minute, then teaches them how to fire, reload, and clean their AK-47s. Later Corporal Gadafi trains the boys to stab their enemies by practicing on a banana tree. The boys stab weakly at first, but improve dramatically when Gadafi tells them to remember that the rebel they may be attacking has done much worse to their parents. That night before bed, Beah reflects that he has learned the underlying lesson - that rebels were evil and deserved to die - quickly and well.