The purpose of manpower planning is to best match future manpower demand and supply in the light of multiple objectives such as economic conditions, production/scale trends, people skills inventory, government regulations, as well as organization history and policies regarding personnel hearing, training, promotion, firing and retirement. One of the essential components of a manpower planning system is manpower forecasting, the process of anticipating the future size and nature of the manpower force. Stochastic models have been widely used in the study of manpower systems with different modes in series like training, promotion, placement, etc. There are many industries and organizations where the skilled personnel are to be recruited and they must be given prior training before employment. In human resource planning the training and induction of the right type of personnel is a pressing problem. In this paper, we consider the optimal solution for the manpower to be kept as reserve inventory at four different nodes in series. Two different models have been discussed. Numerical illustrations are provided using simulation studies.