The origin and development of armies and armed forces is associated with the formation and development of class society and the state. Only with the formation of the first class society, which was the slave system, did the army appear. With the development of productive forces, with changes in production relations, the nature and methods of waging wars changed, and along with this, the forms of organization of the army. Forms of organization of armies, branches and types of troops are usually adapted to the forms and methods of warfare. The militias and standing armies of the slave period gave way to the recruiting and mercenary troops of the feudal era, and the latter gave way to cadre armies of the modern type, existing, with rare exceptions, on the basis of universal conscription.