This thesis studies the Sengoku jidai period with a brief overview on the Onin war which started the so-called century of war. The central focus of the paper is on the unifiers of Japan, Oda Nobunaga, Toyotomi Hideyoshi and Tokugawa Ieyasu. The way they achieved their goals and the methods they used to do so are also studied. In addition, their political, economic and social reforms are mentioned. The goal of the thesis is to see how these three individuals, each using his own specific methods, managed to create a long lasting and stable social order that lasted nearly three hundred years. The research was done using a variety of historical books and journal articles. The results show that the unifiers were shaped by the warring period in which they lived, and consequently, were skilled warriors and military leaders. Each of them possessed the skills required for different stages of the unification. Nobunaga had the ruthlessness and cruelty with which he started to subjugate other provinces. Hideyoshi finished the unification and enacted many laws to better control his subjects, and Ieyasu brought the legislative process to a successful end. It is important to note that they were contemporaries and on relatively good terms. Hideyoshi was Nobunaga’s general, while Ieyasu was allied to him.